diff --git a/index.c b/index.c
index 05420d8..5be102c 100644
--- a/index.c
+++ b/index.c
@@ -60,7 +60,7 @@ void mm_idx_destroy(mm_idx_t *mi)
 			free(mi->seq[i].name);
 		free(mi->seq);
 	} else km_destroy(mi->km);
-	free(mi->B); free(mi->S); free(mi);
+	free(mi->R); free(mi->B); free(mi->S); free(mi);
 }
 
 const uint64_t *mm_idx_get(const mm_idx_t *mi, uint64_t minier, int *n)
@@ -585,3 +585,85 @@ int mm_idx_reader_eof(const mm_idx_reader_t *r) // TODO: in extremely rare cases
 {
 	return r->is_idx? (feof(r->fp.idx) || ftell(r->fp.idx) == r->idx_size) : mm_bseq_eof(r->fp.seq);
 }
+
+#include <ctype.h>
+#include <zlib.h>
+#include "ksort.h"
+#include "kseq.h"
+KSTREAM_DECLARE(gzFile, gzread)
+
+#define sort_key_bed(a) ((a).x)
+KRADIX_SORT_INIT(bed, mm_idx_bed_t, sort_key_bed, 8)
+
+mm_idx_bed_t *mm_idx_read_bed_list(const mm_idx_t *mi, const char *fn, uint32_t *n_)
+{
+	gzFile fp;
+	kstream_t *ks;
+	kstring_t str = {0,0,0};
+	uint32_t n = 0, m = 0;
+	mm_idx_bed_t *r = 0;
+
+	fp = fn && strcmp(fn, "-")? gzopen(fn, "r") : gzdopen(fileno(stdin), "r");
+	if (fp == 0) return 0;
+	ks = ks_init(fp);
+	while (ks_getuntil(ks, KS_SEP_LINE, &str, 0) >= 0) {
+		mm_idx_bed_t t;
+		char *p, *q;
+		int i, id = -1, st = -1, en = -1;
+		for (p = q = str.s, i = 0;; ++p) {
+			if (*p == 0 || isspace(*p)) {
+				int32_t c = *p;
+				*p = 0;
+				if (i == 0) {
+					id = mm_idx_name2id(mi, q);
+					if (id < 0) break; // unknown name; TODO: throw a warning
+				} else if (i == 1) {
+					st = atoi(q);
+					if (st < 0) break;
+				} else if (i == 2) {
+					en = atoi(q);
+					if (en < 0) break;
+				} else break;
+				if (c == 0) break;
+				++i, q = p + 1;
+			}
+		}
+		if (i == 2) en = st + 1;
+		if (i < 2 || st >= en) continue;
+		if (m == n) EXPAND(r, m);
+		t.x = (uint64_t)id << 32 | st, t.end = en, t.idx = -1;
+		r[n++] = t;
+	}
+	ks_destroy(ks);
+	gzclose(fp);
+	*n_ = n;
+	return r;
+}
+
+int mm_idx_attach_bed(mm_idx_t *mi, uint32_t n, mm_idx_bed_t *r) // TODO: check errors
+{
+	radix_sort_bed(r, r + n);
+	mi->R = r, mi->n_R = n;
+	return 0;
+}
+
+int mm_idx_read_bed(mm_idx_t *mi, const char *fn)
+{
+	mm_idx_bed_t *r;
+	uint32_t n;
+	if (mi->h == 0) mm_idx_index_name(mi);
+	r = mm_idx_read_bed_list(mi, fn, &n);
+	return mm_idx_attach_bed(mi, n, r);
+}
+
+int mm_idx_bed_query(const mm_idx_t *mi, uint64_t x)
+{
+	int32_t left = -1, right = mi->n_R;
+	while (right - left > 1) {
+		int32_t mid = left + ((right - left) >> 1);
+		if (mi->R[mid].x > x) right = mid;
+		else if (mi->R[mid].x < x) left = mid;
+		else return mid;
+	}
+	return left;
+}
diff --git a/kseq.h b/kseq.h
index d301ddc..8021e56 100644
--- a/kseq.h
+++ b/kseq.h
@@ -37,6 +37,14 @@
 #define KS_SEP_LINE  2 // line separator: "\n" (Unix) or "\r\n" (Windows)
 #define KS_SEP_MAX   2
 
+#ifndef klib_unused
+#if (defined __clang__ && __clang_major__ >= 3) || (defined __GNUC__ && __GNUC__ >= 3)
+#define klib_unused __attribute__ ((__unused__))
+#else
+#define klib_unused
+#endif
+#endif /* klib_unused */
+
 #define __KS_TYPE(type_t) \
 	typedef struct __kstream_t { \
 		int begin, end; \
@@ -64,7 +72,7 @@
 	}
 
 #define __KS_INLINED(__read) \
-	static inline int ks_getc(kstream_t *ks) \
+	static inline klib_unused int ks_getc(kstream_t *ks) \
 	{ \
 		if (ks->is_eof && ks->begin >= ks->end) return -1; \
 		if (ks->begin >= ks->end) { \
diff --git a/main.c b/main.c
index 0e0812b..07795a9 100644
--- a/main.c
+++ b/main.c
@@ -59,6 +59,7 @@ static ko_longopt_t long_options[] = {
 	{ "paf-no-hit",     ko_no_argument,       333 },
 	{ "split-prefix",   ko_required_argument, 334 },
 	{ "no-end-flt",     ko_no_argument,       335 },
+	{ "bed",            ko_required_argument, 336 },
 	{ "help",           ko_no_argument,       'h' },
 	{ "max-intron-len", ko_required_argument, 'G' },
 	{ "version",        ko_no_argument,       'V' },
@@ -101,7 +102,7 @@ int main(int argc, char *argv[])
 	mm_mapopt_t opt;
 	mm_idxopt_t ipt;
 	int i, c, n_threads = 3, n_parts;
-	char *fnw = 0, *rg = 0, *s;
+	char *fnw = 0, *fn_bed = 0, *rg = 0, *s;
 	FILE *fp_help = stderr;
 	mm_idx_reader_t *idx_rdr;
 	mm_idx_t *mi;
@@ -188,6 +189,7 @@ int main(int argc, char *argv[])
 		else if (c == 333) opt.flag |= MM_F_PAF_NO_HIT; // --paf-no-hit
 		else if (c == 334) opt.split_prefix = o.arg; // --split-prefix
 		else if (c == 335) opt.flag |= MM_F_NO_END_FLT; // --no-end-flt
+		else if (c == 336) fn_bed = o.arg; // --bed-prefer
 		else if (c == 314) { // --frag
 			yes_or_no(&opt, MM_F_FRAG_MODE, o.longidx, o.arg, 1);
 		} else if (c == 315) { // --secondary
@@ -342,6 +344,7 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "[M::%s::%.3f*%.2f] loaded/built the index for %d target sequence(s)\n",
 					__func__, realtime() - mm_realtime0, cputime() / (realtime() - mm_realtime0), mi->n_seq);
 		if (argc != o.ind + 1) mm_mapopt_update(&opt, mi);
+		if (fn_bed) mm_idx_read_bed(mi, fn_bed);
 		if (mm_verbose >= 3) mm_idx_stat(mi);
 		if (!(opt.flag & MM_F_FRAG_MODE)) {
 			for (i = o.ind + 1; i < argc; ++i)
diff --git a/minimap.h b/minimap.h
index 27ba911..6bae3fb 100644
--- a/minimap.h
+++ b/minimap.h
@@ -58,13 +58,20 @@ typedef struct {
 	uint32_t len;    // length
 } mm_idx_seq_t;
 
+typedef struct {
+	uint64_t x;
+	int32_t end, idx;
+} mm_idx_bed_t;
+
 typedef struct {
 	int32_t b, w, k, flag;
 	uint32_t n_seq;            // number of reference sequences
 	int32_t index;
+	uint32_t n_R;
 	mm_idx_seq_t *seq;         // sequence name, length and offset
 	uint32_t *S;               // 4-bit packed sequence
 	struct mm_idx_bucket_s *B; // index (hidden)
+	mm_idx_bed_t *R;
 	void *km, *h;
 } mm_idx_t;
 
@@ -365,6 +372,9 @@ int mm_idx_getseq(const mm_idx_t *mi, uint32_t rid, uint32_t st, uint32_t en, ui
 void mm_mapopt_init(mm_mapopt_t *opt);
 mm_idx_t *mm_idx_build(const char *fn, int w, int k, int flag, int n_threads);
 
+int mm_idx_read_bed(mm_idx_t *mi, const char *fn);
+int mm_idx_bed_query(const mm_idx_t *mi, uint64_t x);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/mmpriv.h b/mmpriv.h
index f847445..9e4a95b 100644
--- a/mmpriv.h
+++ b/mmpriv.h
@@ -31,6 +31,13 @@
 #define MALLOC(type, len) ((type*)malloc((len) * sizeof(type)))
 #define CALLOC(type, len) ((type*)calloc((len), sizeof(type)))
 
+#define REALLOC(ptr, len) ((ptr) = (__typeof__(ptr))realloc((ptr), (len) * sizeof(*(ptr))))
+
+#define EXPAND(a, m) do { \
+		(m) = (m)? (m) + ((m)>>1) : 16; \
+		REALLOC((a), (m)); \
+	} while (0)
+
 #ifdef __cplusplus
 extern "C" {
 #endif