diff --git a/cmd/grpcurl/grpcurl.go b/cmd/grpcurl/grpcurl.go
index cc5cfa1..70712a6 100644
--- a/cmd/grpcurl/grpcurl.go
+++ b/cmd/grpcurl/grpcurl.go
@@ -9,6 +9,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -126,6 +127,7 @@ var (
 		an error to use both -authority and -servername (though this will be
 		permitted if they are both set to the same value, to increase backwards
 		compatibility with earlier releases that allowed both to be set).`))
+	reflection = optionalBoolFlag{val: true}
 )
 
 func init() {
@@ -168,6 +170,12 @@ func init() {
 		order given. If no import paths are given, all files (including all
 		imports) must be provided as -proto flags, and grpcurl will attempt to
 		resolve all import statements from the set of file names given.`))
+	flags.Var(&reflection, "use-reflection", prettify(`
+		When true, server reflection will be used to determine the RPC schema.
+		Defaults to true unless a -proto or -protoset option is provided. If
+		-use-reflection is used in combination with a -proto or -protoset flag,
+		the provided descriptor sources will be used in addition to server
+		reflection to resolve messages and extensions.`))
 }
 
 type multiString []string
@@ -181,6 +189,49 @@ func (s *multiString) Set(value string) error {
 	return nil
 }
 
+// Uses a file source as a fallback for resolving symbols and extensions, but
+// only uses the reflection source for listing services
+type compositeSource struct {
+	reflection grpcurl.DescriptorSource
+	file       grpcurl.DescriptorSource
+}
+
+func (cs compositeSource) ListServices() ([]string, error) {
+	return cs.reflection.ListServices()
+}
+
+func (cs compositeSource) FindSymbol(fullyQualifiedName string) (desc.Descriptor, error) {
+	d, err := cs.reflection.FindSymbol(fullyQualifiedName)
+	if err == nil {
+		return d, nil
+	}
+	return cs.file.FindSymbol(fullyQualifiedName)
+}
+
+func (cs compositeSource) AllExtensionsForType(typeName string) ([]*desc.FieldDescriptor, error) {
+	exts, err := cs.reflection.AllExtensionsForType(typeName)
+	if err != nil {
+		// On error fall back to file source
+		return cs.file.AllExtensionsForType(typeName)
+	}
+	// Track the tag numbers from the reflection source
+	tags := make(map[int32]bool)
+	for _, ext := range exts {
+		tags[ext.GetNumber()] = true
+	}
+	fileExts, err := cs.file.AllExtensionsForType(typeName)
+	if err != nil {
+		return exts, nil
+	}
+	for _, ext := range fileExts {
+		// Prioritize extensions found via reflection
+		if !tags[ext.GetNumber()] {
+			exts = append(exts, ext)
+		}
+	}
+	return exts, nil
+}
+
 func main() {
 	flags.Usage = usage
 	flags.Parse(os.Args[1:])
@@ -288,6 +339,14 @@ func main() {
 	if len(importPaths) > 0 && len(protoFiles) == 0 {
 		warn("The -import-path argument is not used unless -proto files are used.")
 	}
+	if !reflection.val && len(protoset) == 0 && len(protoFiles) == 0 {
+		fail(nil, "No protoset files or proto files specified and -use-reflection set to false.")
+	}
+
+	// Protoset or protofiles provided and -use-reflection unset
+	if !reflection.set && (len(protoset) > 0 || len(protoFiles) > 0) {
+		reflection.val = false
+	}
 
 	ctx := context.Background()
 	if *maxTime > 0 {
@@ -372,24 +431,33 @@ func main() {
 	var cc *grpc.ClientConn
 	var descSource grpcurl.DescriptorSource
 	var refClient *grpcreflect.Client
+	var fileSource grpcurl.DescriptorSource
 	if len(protoset) > 0 {
 		var err error
-		descSource, err = grpcurl.DescriptorSourceFromProtoSets(protoset...)
+		fileSource, err = grpcurl.DescriptorSourceFromProtoSets(protoset...)
 		if err != nil {
 			fail(err, "Failed to process proto descriptor sets.")
 		}
 	} else if len(protoFiles) > 0 {
 		var err error
-		descSource, err = grpcurl.DescriptorSourceFromProtoFiles(importPaths, protoFiles...)
+		fileSource, err = grpcurl.DescriptorSourceFromProtoFiles(importPaths, protoFiles...)
 		if err != nil {
 			fail(err, "Failed to process proto source files.")
 		}
-	} else {
+	}
+	if reflection.val {
 		md := grpcurl.MetadataFromHeaders(append(addlHeaders, reflHeaders...))
 		refCtx := metadata.NewOutgoingContext(ctx, md)
 		cc = dial()
 		refClient = grpcreflect.NewClient(refCtx, reflectpb.NewServerReflectionClient(cc))
-		descSource = grpcurl.DescriptorSourceFromServer(ctx, refClient)
+		reflSource := grpcurl.DescriptorSourceFromServer(ctx, refClient)
+		if fileSource != nil {
+			descSource = compositeSource{reflSource, fileSource}
+		} else {
+			descSource = reflSource
+		}
+	} else {
+		descSource = fileSource
 	}
 
 	// arrange for the RPCs to be cleanly shutdown
@@ -672,3 +740,28 @@ func writeProtoset(descSource grpcurl.DescriptorSource, symbols ...string) error
 	defer f.Close()
 	return grpcurl.WriteProtoset(f, descSource, symbols...)
 }
+
+type optionalBoolFlag struct {
+	set, val bool
+}
+
+func (f *optionalBoolFlag) String() string {
+	if !f.set {
+		return "unset"
+	}
+	return strconv.FormatBool(f.val)
+}
+
+func (f *optionalBoolFlag) Set(s string) error {
+	v, err := strconv.ParseBool(s)
+	if err != nil {
+		return err
+	}
+	f.set = true
+	f.val = v
+	return nil
+}
+
+func (f *optionalBoolFlag) IsBoolFlag() bool {
+	return true
+}