diff --git a/Makefile b/Makefile
index 3733b59..e773d2d 100644
--- a/Makefile
+++ b/Makefile
@@ -14,8 +14,8 @@ chibicc: $(OBJS)
 $(OBJS): chibicc.h
 
 test/%.exe: chibicc test/%.c
-	$(CC) -o- -E -P -C test/$*.c | ./chibicc -o test/$*.s -
-	$(CC) -o $@ test/$*.s -xc test/common
+	$(CC) -o- -E -P -C test/$*.c | ./chibicc -o test/$*.o -
+	$(CC) -o $@ test/$*.o -xc test/common
 
 test: $(TESTS)
 	for i in $^; do echo $$i; ./$$i || exit 1; echo; done
@@ -28,15 +28,15 @@ test-all: test test-stage2
 stage2/chibicc: $(OBJS:%=stage2/%)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-stage2/%.s: chibicc self.py %.c
+stage2/%.o: chibicc self.py %.c
 	mkdir -p stage2/test
 	./self.py chibicc.h $*.c > stage2/$*.c
-	./chibicc -o stage2/$*.s stage2/$*.c
+	./chibicc -o stage2/$*.o stage2/$*.c
 
 stage2/test/%.exe: stage2/chibicc test/%.c
 	mkdir -p stage2/test
-	$(CC) -o- -E -P -C test/$*.c | ./stage2/chibicc -o stage2/test/$*.s -
-	$(CC) -o $@ stage2/test/$*.s -xc test/common
+	$(CC) -o- -E -P -C test/$*.c | ./stage2/chibicc -o stage2/test/$*.o -
+	$(CC) -o $@ stage2/test/$*.o -xc test/common
 
 test-stage2: $(TESTS:test/%=stage2/test/%)
 	for i in $^; do echo $$i; ./$$i || exit 1; echo; done
diff --git a/chibicc.h b/chibicc.h
index ae71b4a..d2c3236 100644
--- a/chibicc.h
+++ b/chibicc.h
@@ -2,6 +2,7 @@
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
+#include <libgen.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -25,6 +26,13 @@ typedef struct Relocation Relocation;
 // strings.c
 //
 
+typedef struct {
+  char **data;
+  int capacity;
+  int len;
+} StringArray;
+
+void strarray_push(StringArray *arr, char *s);
 char *format(char *fmt, ...);
 
 //
diff --git a/main.c b/main.c
index 02e8fcf..a16eae5 100644
--- a/main.c
+++ b/main.c
@@ -1,10 +1,12 @@
 #include "chibicc.h"
 
+static bool opt_S;
 static bool opt_cc1;
 static bool opt_hash_hash_hash;
 static char *opt_o;
 
 static char *input_path;
+static StringArray tmpfiles;
 
 static void usage(int status) {
   fprintf(stderr, "chibicc [ -o <path> ] <file>\n");
@@ -38,6 +40,11 @@ static void parse_args(int argc, char **argv) {
       continue;
     }
 
+    if (!strcmp(argv[i], "-S")) {
+      opt_S = true;
+      continue;
+    }
+
     if (argv[i][0] == '-' && argv[i][1] != '\0')
       error("unknown argument: %s", argv[i]);
 
@@ -58,6 +65,31 @@ static FILE *open_file(char *path) {
   return out;
 }
 
+// Replace file extension
+static char *replace_extn(char *tmpl, char *extn) {
+  char *filename = basename(strdup(tmpl));
+  char *dot = strrchr(filename, '.');
+  if (dot)
+    *dot = '\0';
+  return format("%s%s", filename, extn);
+}
+
+static void cleanup(void) {
+  for (int i = 0; i < tmpfiles.len; i++)
+    unlink(tmpfiles.data[i]);
+}
+
+static char *create_tmpfile(void) {
+  char *path = strdup("/tmp/chibicc-XXXXXX");
+  int fd = mkstemp(path);
+  if (fd == -1)
+    error("mkstemp failed: %s", strerror(errno));
+  close(fd);
+
+  strarray_push(&tmpfiles, path);
+  return path;
+}
+
 static void run_subprocess(char **argv) {
   // If -### is given, dump the subprocess's command line.
   if (opt_hash_hash_hash) {
@@ -81,10 +113,19 @@ static void run_subprocess(char **argv) {
     exit(1);
 }
 
-static void run_cc1(int argc, char **argv) {
+static void run_cc1(int argc, char **argv, char *input, char *output) {
   char **args = calloc(argc + 10, sizeof(char *));
   memcpy(args, argv, argc * sizeof(char *));
   args[argc++] = "-cc1";
+
+  if (input)
+    args[argc++] = input;
+
+  if (output) {
+    args[argc++] = "-o";
+    args[argc++] = output;
+  }
+
   run_subprocess(args);
 }
 
@@ -99,7 +140,13 @@ static void cc1(void) {
   codegen(prog, out);
 }
 
+static void assemble(char *input, char *output) {
+  char *cmd[] = {"as", "-c", input, "-o", output, NULL};
+  run_subprocess(cmd);
+}
+
 int main(int argc, char **argv) {
+  atexit(cleanup);
   parse_args(argc, argv);
 
   if (opt_cc1) {
@@ -107,6 +154,23 @@ int main(int argc, char **argv) {
     return 0;
   }
 
-  run_cc1(argc, argv);
+  char *output;
+  if (opt_o)
+    output = opt_o;
+  else if (opt_S)
+    output = replace_extn(input_path, ".s");
+  else
+    output = replace_extn(input_path, ".o");
+
+  // If -S is given, assembly text is the final output.
+  if (opt_S) {
+    run_cc1(argc, argv, input_path, output);
+    return 0;
+  }
+
+  // Otherwise, run the assembler to assemble our output.
+  char *tmpfile = create_tmpfile();
+  run_cc1(argc, argv, input_path, tmpfile);
+  assemble(tmpfile, output);
   return 0;
 }
diff --git a/strings.c b/strings.c
index 485d033..9e67428 100644
--- a/strings.c
+++ b/strings.c
@@ -1,5 +1,21 @@
 #include "chibicc.h"
 
+void strarray_push(StringArray *arr, char *s) {
+  if (!arr->data) {
+    arr->data = calloc(8, sizeof(char *));
+    arr->capacity = 8;
+  }
+
+  if (arr->capacity == arr->len) {
+    arr->data = realloc(arr->data, sizeof(char *) * arr->capacity * 2);
+    arr->capacity *= 2;
+    for (int i = arr->len; i < arr->capacity; i++)
+      arr->data[i] = NULL;
+  }
+
+  arr->data[arr->len++] = s;
+}
+
 // Takes a printf-style format string and returns a formatted string.
 char *format(char *fmt, ...) {
   char *buf;
diff --git a/test/driver.sh b/test/driver.sh
index a35dc71..d30c46d 100755
--- a/test/driver.sh
+++ b/test/driver.sh
@@ -24,4 +24,19 @@ check -o
 $chibicc --help 2>&1 | grep -q chibicc
 check --help
 
+# -S
+echo 'int main() {}' | $chibicc -S -o - - | grep -q 'main:'
+check -S
+
+# Default output file
+rm -f $tmp/out.o $tmp/out.s
+echo 'int main() {}' > $tmp/out.c
+(cd $tmp; $OLDPWD/$chibicc out.c)
+[ -f $tmp/out.o ]
+check 'default output file'
+
+(cd $tmp; $OLDPWD/$chibicc -S out.c)
+[ -f $tmp/out.s ]
+check 'default output file'
+
 echo OK