diff --git a/callgraphutil/dot.go b/callgraphutil/dot.go
new file mode 100644
index 0000000..07b8609
--- /dev/null
+++ b/callgraphutil/dot.go
@@ -0,0 +1,88 @@
+package callgraphutil
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+
+	"golang.org/x/tools/go/callgraph"
+)
+
+// WriteDOT writes the given callgraph.Graph to the given io.Writer in the
+// DOT format, which can be used to generate a visual representation of the
+// call graph using Graphviz.
+func WriteDOT(w io.Writer, g *callgraph.Graph) error {
+	b := bufio.NewWriter(w)
+	defer b.Flush()
+
+	b.WriteString("digraph callgraph {\n")
+	b.WriteString("\tgraph [fontname=\"Helvetica\", overlap=false normalize=true];\n")
+	b.WriteString("\tnode [fontname=\"Helvetica\" shape=box];\n")
+	b.WriteString("\tedge [fontname=\"Helvetica\"];\n")
+
+	edges := []*callgraph.Edge{}
+
+	nodesByPkg := map[string][]*callgraph.Node{}
+
+	addPkgNode := func(n *callgraph.Node) {
+		// TODO: fix this so there's not so many "shared" functions?
+		//
+		// It is a bit of a hack, but it works for now.
+		var pkgPath string
+		if n.Func.Pkg != nil {
+			pkgPath = n.Func.Pkg.Pkg.Path()
+		} else {
+			pkgPath = "shared"
+		}
+
+		// Check if the package already exists.
+		if _, ok := nodesByPkg[pkgPath]; !ok {
+			// If not, create it.
+			nodesByPkg[pkgPath] = []*callgraph.Node{}
+		}
+		nodesByPkg[pkgPath] = append(nodesByPkg[pkgPath], n)
+	}
+
+	// Check if root node exists, if so, write it.
+	if g.Root != nil {
+		b.WriteString(fmt.Sprintf("\troot = %d;\n", g.Root.ID))
+	}
+
+	// Process nodes and edges.
+	for _, n := range g.Nodes {
+		// Add node to map of nodes by package.
+		addPkgNode(n)
+
+		// Add edges
+		edges = append(edges, n.Out...)
+	}
+
+	// Write nodes by package.
+	for pkg, nodes := range nodesByPkg {
+		// Make the pkg name sugraph cluster friendly (remove dots, dashes, and slashes).
+		clusterName := strings.Replace(pkg, ".", "_", -1)
+		clusterName = strings.Replace(clusterName, "/", "_", -1)
+		clusterName = strings.Replace(clusterName, "-", "_", -1)
+
+		// NOTE: even if we're using a subgraph cluster, it may not be
+		// respected by all Graphviz layout engines. For example, the
+		// "dot" engine will respect the cluster, but the "sfdp" engine
+		// will not.
+		b.WriteString(fmt.Sprintf("\tsubgraph cluster_%s {\n", clusterName))
+		b.WriteString(fmt.Sprintf("\t\tlabel=%q;\n", pkg))
+		for _, n := range nodes {
+			b.WriteString(fmt.Sprintf("\t\t%d [label=%q];\n", n.ID, n.Func))
+		}
+		b.WriteString("\t}\n")
+	}
+
+	// Write edges.
+	for _, e := range edges {
+		b.WriteString(fmt.Sprintf("\t%d -> %d;\n", e.Caller.ID, e.Callee.ID))
+	}
+
+	b.WriteString("}\n")
+
+	return nil
+}
diff --git a/callgraphutil/dot_test.go b/callgraphutil/dot_test.go
new file mode 100644
index 0000000..8cea70c
--- /dev/null
+++ b/callgraphutil/dot_test.go
@@ -0,0 +1,196 @@
+package callgraphutil_test
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/picatz/taint/callgraphutil"
+	"golang.org/x/tools/go/callgraph"
+	"golang.org/x/tools/go/packages"
+	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/go/ssa/ssautil"
+)
+
+func cloneGitHubRepository(ctx context.Context, ownerName, repoName string) (string, string, error) {
+	// Get the owner and repo part of the URL.
+	ownerAndRepo := ownerName + "/" + repoName
+
+	// Get the directory path.
+	dir := filepath.Join(os.TempDir(), "taint", "github", ownerAndRepo)
+
+	// Check if the directory exists.
+	_, err := os.Stat(dir)
+	if err == nil {
+		// If the directory exists, we'll assume it's a valid repository,
+		// and return the directory. Open the directory to
+		repo, err := git.PlainOpen(dir)
+		if err != nil {
+			return dir, "", fmt.Errorf("%w", err)
+		}
+
+		// Get the repository's HEAD.
+		head, err := repo.Head()
+		if err != nil {
+			return dir, "", fmt.Errorf("%w", err)
+		}
+
+		return dir, head.Hash().String(), nil
+	}
+
+	// Clone the repository.
+	repo, err := git.PlainCloneContext(ctx, dir, false, &git.CloneOptions{
+		URL:          fmt.Sprintf("https://github.com/%s", ownerAndRepo),
+		Depth:        1,
+		Tags:         git.NoTags,
+		SingleBranch: true,
+	})
+	if err != nil {
+		return dir, "", fmt.Errorf("%w", err)
+	}
+
+	// Get the repository's HEAD.
+	head, err := repo.Head()
+	if err != nil {
+		return dir, "", fmt.Errorf("%w", err)
+	}
+
+	return dir, head.Hash().String(), nil
+}
+
+func loadPackages(ctx context.Context, dir, pattern string) ([]*packages.Package, error) {
+	loadMode :=
+		packages.NeedName |
+			packages.NeedDeps |
+			packages.NeedFiles |
+			packages.NeedModule |
+			packages.NeedTypes |
+			packages.NeedImports |
+			packages.NeedSyntax |
+			packages.NeedTypesInfo
+		// packages.NeedTypesSizes |
+		// packages.NeedCompiledGoFiles |
+		// packages.NeedExportFile |
+		// packages.NeedEmbedPatterns
+
+	// parseMode := parser.ParseComments
+	parseMode := parser.SkipObjectResolution
+
+	// patterns := []string{dir}
+	patterns := []string{pattern}
+	// patterns := []string{"all"}
+
+	pkgs, err := packages.Load(&packages.Config{
+		Mode:    loadMode,
+		Context: ctx,
+		Env:     os.Environ(),
+		Dir:     dir,
+		Tests:   false,
+		ParseFile: func(fset *token.FileSet, filename string, src []byte) (*ast.File, error) {
+			return parser.ParseFile(fset, filename, src, parseMode)
+		},
+	}, patterns...)
+	if err != nil {
+		return nil, err
+	}
+
+	return pkgs, nil
+
+}
+
+func loadSSA(ctx context.Context, pkgs []*packages.Package) (mainFn *ssa.Function, srcFns []*ssa.Function, err error) {
+	ssaBuildMode := ssa.InstantiateGenerics // ssa.SanityCheckFunctions | ssa.GlobalDebug
+
+	// Analyze the package.
+	ssaProg, ssaPkgs := ssautil.Packages(pkgs, ssaBuildMode)
+
+	ssaProg.Build()
+
+	for _, pkg := range ssaPkgs {
+		pkg.Build()
+	}
+
+	mainPkgs := ssautil.MainPackages(ssaPkgs)
+
+	mainFn = mainPkgs[0].Members["main"].(*ssa.Function)
+
+	for _, pkg := range ssaPkgs {
+		for _, fn := range pkg.Members {
+			if fn.Object() == nil {
+				continue
+			}
+
+			if fn.Object().Name() == "_" {
+				continue
+			}
+
+			pkgFn := pkg.Func(fn.Object().Name())
+			if pkgFn == nil {
+				continue
+			}
+
+			var addAnons func(f *ssa.Function)
+			addAnons = func(f *ssa.Function) {
+				srcFns = append(srcFns, f)
+				for _, anon := range f.AnonFuncs {
+					addAnons(anon)
+				}
+			}
+			addAnons(pkgFn)
+		}
+	}
+
+	if mainFn == nil {
+		err = fmt.Errorf("failed to find main function")
+		return
+	}
+
+	return
+}
+
+func loadCallGraph(ctx context.Context, mainFn *ssa.Function, srcFns []*ssa.Function) (*callgraph.Graph, error) {
+	cg, err := callgraphutil.NewGraph(mainFn, srcFns...)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create new callgraph: %w", err)
+	}
+
+	return cg, nil
+}
+
+func TestWriteDOT(t *testing.T) {
+	repo, _, err := cloneGitHubRepository(context.Background(), "picatz", "taint")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pkgs, err := loadPackages(context.Background(), repo, "./...")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mainFn, srcFns, err := loadSSA(context.Background(), pkgs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cg, err := loadCallGraph(context.Background(), mainFn, srcFns)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	output := &bytes.Buffer{}
+
+	err = callgraphutil.WriteDOT(output, cg)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fmt.Println(output.String())
+}