diff --git a/src/pbsim.cpp b/src/pbsim.cpp
index 82b0a4c..36ede84 100644
--- a/src/pbsim.cpp
+++ b/src/pbsim.cpp
@@ -12,6 +12,7 @@
 #include <limits.h>
 #include <sys/time.h>
 #include <sys/resource.h>
+#include <random>
 
 #define SUCCEEDED 1
 #define FAILED 0
@@ -61,6 +62,7 @@ struct sim_t {
   char *hmm_model_file;
   char *profile_id, *profile_fq, *profile_stats;
   char *id_prefix;
+  int circular;
 };
 
 // FASTQ
@@ -190,6 +192,7 @@ int main (int argc, char** argv) {
     {"sample-profile-id", 1, NULL, 0},
     {"seed", 1, NULL, 0},
     {"id-prefix", 1, NULL, 0},
+    {"circular", 1, NULL, 0},
     {0, 0, 0, 0}
   };
 
@@ -352,6 +355,14 @@ int main (int argc, char** argv) {
         strcpy(sim.id_prefix, optarg);
         break;
 
+      case 15:
+        sim.circular =  atof(optarg);
+        if (sim.circular != TRUE && sim.circular != FALSE){
+          fprintf(stderr, "ERROR (invalid value): --circular can be either set on 1 or 0\n");
+          exit(-1);
+        }
+        break;
+
       default:
         break;
       }
@@ -976,6 +987,11 @@ int set_sim_param() {
     sim.del_ratio = 40;
   }
 
+  // circular 
+  if (!(sim.set_flg[15])) {
+    sim.circular = FALSE;
+  }
+
   sum = sim.sub_ratio + sim.ins_ratio + sim.del_ratio;
   sim.sub_rate = (double)sim.sub_ratio / sum;
   sim.ins_rate = (double)sim.ins_ratio / sum;
@@ -1698,6 +1714,8 @@ void print_sim_param(int seed) {
     sim.sub_ratio, sim.ins_ratio, sim.del_ratio);
 
   fprintf(stderr, "seed : %d\n", seed);
+  fprintf(stderr, "circular: %d\n", sim.circular);
+
 
   fprintf(stderr, "\n");
 }
@@ -1768,6 +1786,11 @@ int mutate() {
   long offset, seq_offset, maf_offset;
   long del_num_total, pos;
 
+  // sample from uniform distribution for offsets on circular genome
+  std::random_device rd;  //Will be used to obtain a seed for the random number engine
+  std::mt19937 gen(rd()); //Standard mersenne_twister_engine seeded with rd()
+  std::uniform_int_distribution<> distribution(0,ref.len-1);
+
   len = strlen(mut.qc);
   if (mut.tmp_len_max < len) {
     len = mut.tmp_len_max;
@@ -1806,7 +1829,11 @@ int mutate() {
     offset = 0;
     len = ref.len;
   } else {
-    offset = rand() % (ref.len - len + 1);
+    if (sim.circular == TRUE){
+      offset = distribution(gen);
+    }else {
+      offset = rand() % (ref.len - len + 1);
+    }
   }
 
   mut.seq_left = offset + 1;
@@ -1816,14 +1843,25 @@ int mutate() {
     mut.seq_strand = '+';
 
     for (i=0; i<len; i++) {
-      nt = toupper(ref.seq[offset + i]);
+      if (sim.circular == TRUE){
+        // if circular genome
+        nt = toupper(ref.seq[(offset + i)%(ref.len - 1)]);
+      } else{
+        nt = toupper(ref.seq[offset + i]);
+      }
       mut.seq[i] = nt;
     }
   } else {
     mut.seq_strand = '-';
 
     for (i=0; i<len; i++) {
-      nt = toupper(ref.seq[offset + i]);
+
+      if (sim.circular == TRUE){
+        // if circular genome
+        nt = toupper(ref.seq[(offset + i)%(ref.len - 1)]);
+      } else{
+        nt = toupper(ref.seq[offset + i]);
+      }
 
       if (nt == 'A') {
         mut.seq[len-1-i] = 'T';
@@ -2069,6 +2107,8 @@ void print_help() {
   fprintf(stderr, "  --length-mean        mean of length model (9000.0).\n");
   fprintf(stderr, "  --length-sd          standard deviation of length model (7000.0).\n");
   fprintf(stderr, "  --accuracy-mean      mean of accuracy model (0.85).\n");
+  fprintf(stderr, "  --circular           circular genome (0).\n");
+  fprintf(stderr, "                       to enable this use 1.\n");
   fprintf(stderr, "\n");
 }