diff --git a/Makefile b/Makefile
index c579ff4..b00d018 100644
--- a/Makefile
+++ b/Makefile
@@ -25,6 +25,7 @@ obj-y += source/core/flash.o
 
 obj-y += source/fs/mufs/block.o
 obj-y += source/fs/mufs/dir.o
+obj-y += source/fs/mufs/file.o
 obj-y += source/fs/mufs/super.o
 obj-y += source/fs/mufs/tree.o
 
diff --git a/include/fs/mufs.h b/include/fs/mufs.h
index 65c3638..9e02382 100644
--- a/include/fs/mufs.h
+++ b/include/fs/mufs.h
@@ -3,6 +3,7 @@
 struct flash_dev;
 struct mufs;
 struct mufs_dir;
+struct mufs_file;
 
 struct mufs_tree {
 	struct mufs *fs;
@@ -33,3 +34,9 @@ struct mufs_dir *mufs_opendir(struct mufs *fs, const char *path);
 void mufs_closedir(struct mufs_dir *dir);
 int mufs_readdir(struct mufs_dir *dir, struct mufs_dirent *dirent);
 int mufs_mkdir(struct mufs *fs, const char *path);
+
+int mufs_create(struct mufs *fs, const char *path);
+struct mufs_file *mufs_open(struct mufs *fs, const char *path);
+void mufs_close(struct mufs_file *file);
+size_t mufs_read(struct mufs_file *file, void *data, size_t len);
+size_t mufs_write(struct mufs_file *file, const void *data, size_t len);
diff --git a/source/fs/mufs/file.c b/source/fs/mufs/file.c
new file mode 100644
index 0000000..4786b3c
--- /dev/null
+++ b/source/fs/mufs/file.c
@@ -0,0 +1,143 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <flash.h>
+#include <macros.h>
+
+#include <fs/mufs.h>
+
+#include "dir.h"
+#include "tree.h"
+
+struct mufs_file {
+	struct mufs *fs;
+	struct mufs_tree *tree;
+	uint32_t va;
+};
+
+int mufs_create(struct mufs *fs, const char *path)
+{
+	struct mufs_dirent dirent;
+	struct mufs_tree *tree;
+	size_t len;
+	char *s;
+	char *name;
+
+	if (!path || *path == '\0')
+		return -1;
+
+	if (!(s = mufs_abspath(path)))
+		return -1;
+
+	/* TODO: already exists. */
+	if (resolve_path(fs, s)) {
+		free(s);
+		return 0;
+	}
+
+	if (!(name = strrchr(s, '/'))) {
+		name = s;
+		s = "/";
+	} else {
+		*name++ = '\0';
+	}
+
+	if (*name == '\0')
+		return -1;
+
+	if (!(tree = resolve_path(fs, s)))
+		return -1;
+
+	len = min(strlen(name), sizeof(dirent.path) - 1);
+	memcpy(dirent.path, name, len);
+	dirent.path[len] = '\0';
+	dirent.type = MUFS_FILE;
+
+	dirent.tree.fs = fs;
+	dirent.tree.file_size = 0;
+	dirent.tree.root = 0;
+	dirent.tree.depth = 0;
+
+	if (!is_aligned(tree->file_size, fs->dev->log2_block_size) &&
+		write_dirent(tree, tree->file_size, &dirent) > 0)
+		return 0;
+
+	if (write_dirent(tree, align_up(tree->file_size,
+		fs->dev->log2_block_size), &dirent) > 0)
+		return 0;
+
+	return -1;
+}
+
+struct mufs_file *mufs_open(struct mufs *fs, const char *path)
+{
+	struct mufs_file *file;
+
+	if (!(file = malloc(sizeof(*file))))
+		return NULL;
+
+	file->fs = fs;
+
+	if (!(file->tree = resolve_path(fs, path)))
+		goto err_free_file;
+
+	file->va = 0;
+
+	return file;
+
+err_free_file:
+	free(file);
+	return NULL;
+}
+
+void mufs_close(struct mufs_file *file)
+{
+	if (!file)
+		return;
+
+	free(file);
+}
+
+size_t mufs_read(struct mufs_file *file, void *data, size_t len)
+{
+	size_t ret;
+
+	if (!file || !data || !len)
+		return 0;
+
+	if (!(ret = mufs_tree_read(file->tree, data, file->va, len)))
+		return 0;
+
+	file->va += ret;
+
+	return ret;
+}
+
+size_t mufs_write(struct mufs_file *file, const void *data, size_t len)
+{
+	size_t ret;
+
+	if (!file || !data || !len)
+		return 0;
+
+	if (!(ret = mufs_tree_write(file->tree, (void *)data, file->va, len)))
+		return 0;
+
+	file->va += ret;
+
+	if (file->tree->file_size <= file->va) {
+		struct mufs_dtree dtree;
+
+		dtree.file_size = file->tree->file_size;
+		dtree.root = file->tree->root;
+		dtree.depth = file->tree->depth;
+
+		if (flash_write(file->fs->dev, file->tree->va, &dtree,
+			sizeof dtree) == 0)
+			return 0;
+	}
+
+	return ret;
+}