diff --git a/include/picrin/irep.h b/include/picrin/irep.h
index f8b62885..e9efe627 100644
--- a/include/picrin/irep.h
+++ b/include/picrin/irep.h
@@ -3,6 +3,8 @@
 
 enum pic_instruction {
   OP_PUSHNIL,
+  OP_PUSHTRUE,
+  OP_PUSHFALSE,
   OP_PUSHNUM,
   OP_PUSHUNDEF,
   OP_GREF,
diff --git a/include/picrin/value.h b/include/picrin/value.h
index 2bca6f0a..fc627138 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -3,8 +3,10 @@
 
 enum pic_vtype {
   PIC_VTYPE_NIL,
-  PIC_VTYPE_FLOAT,
+  PIC_VTYPE_TRUE,
+  PIC_VTYPE_FALSE,
   PIC_VTYPE_UNDEF,
+  PIC_VTYPE_FLOAT,
   PIC_VTYPE_HEAP
 };
 
@@ -19,6 +21,7 @@ typedef struct {
 enum pic_tt {
   /* immediate */
   PIC_TT_NIL,
+  PIC_TT_BOOL,
   PIC_TT_FLOAT,
   PIC_TT_UNDEF,
   /* heap */
@@ -54,12 +57,17 @@ struct pic_proc;
 enum pic_tt pic_type(pic_value);
 
 pic_value pic_nil_value();
+pic_value pic_true_value();
+pic_value pic_false_value();
+pic_value pic_bool_value(bool);
 pic_value pic_undef_value();
 pic_value pic_obj_value(void *);
 pic_value pic_float_value(double);
 
 #define pic_float(v) ((v).u.f)
 
-#define pic_nil_p(v) (pic_type(v) == PIC_TT_NIL)
+#define pic_nil_p(v) ((v).type == PIC_VTYPE_NIL)
+#define pic_true_p(v) ((v).type == PIC_VTYPE_TRUE)
+#define pic_false_p(v) ((v).type == PIC_VTYPE_FALSE)
 
 #endif
diff --git a/src/parse.y b/src/parse.y
index bff7e832..5582c769 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -19,7 +19,7 @@ struct parser_control {
 }
 
 %token tLPAREN tRPAREN tDOT
-%token <datum> tSYMBOL tNUMBER
+%token <datum> tSYMBOL tNUMBER tBOOLEAN
 
 %type <datum> datum simple_datum symbol compound_datum
 %type <datum> number list list_tail
@@ -45,6 +45,7 @@ datum
 simple_datum
 	: symbol
 	| number
+	| boolean
 ;
 
 symbol
@@ -58,6 +59,10 @@ number
 	: tNUMBER
 ;
 
+boolean
+	: tBOOLEAN
+;
+
 compound_datum
 	: list
 ;
diff --git a/src/port.c b/src/port.c
index e6ddbbb0..08a2b190 100644
--- a/src/port.c
+++ b/src/port.c
@@ -11,6 +11,12 @@ pic_debug(pic_state *pic, pic_value obj)
   case PIC_TT_NIL:
     printf("()");
     break;
+  case PIC_TT_BOOL:
+    if (pic_true_p(obj))
+      printf("#t");
+    else
+      printf("#f");
+    break;
   case PIC_TT_PAIR:
     printf("(");
     pic_debug(pic, pic_car(pic, obj));
diff --git a/src/scan.l b/src/scan.l
index fe82f6c3..22765a59 100644
--- a/src/scan.l
+++ b/src/scan.l
@@ -14,6 +14,9 @@ struct parser_control {
 
 %option nounput
 
+  /* boolean */
+boolean		#t|#f|#true|#false
+
   /* symbol */
 identifier	[a-z0-9A-Z+-/*?<=>_]+
 
@@ -22,13 +25,14 @@ digit		[0-9]
 real		{sign}{ureal}|{infnan}
 ureal		{digit}+|\.{digit}+|{digit}+\.{digit}*
 sign		[+-]?
-infnan		(\+inf\.0|-inf\.0|\+nan\.0|-nan\.0)
+infnan		"+inf.0"|"-inf.0"|"+nan.0"|"-nan.0"
 
 %%
 
 [ \t\n\r]	/* skip whitespace */
 "("		return tLPAREN;
 ")"		return tRPAREN;
+{boolean}	{ yylval.datum = pic_bool_value(strcmp(yytext, "#t") == 0 || strcmp(yytext, "#true") == 0); return tBOOLEAN; }
 {real} 		{ yylval.datum = pic_float_value(atof(yytext)); return tNUMBER; }
 {identifier}	{ yylval.datum = pic_intern_cstr(p->pic, yytext); return tSYMBOL; }
 
diff --git a/src/value.c b/src/value.c
index 9b8becfd..52aca41a 100644
--- a/src/value.c
+++ b/src/value.c
@@ -8,6 +8,9 @@ pic_type(pic_value v)
   switch (v.type) {
   case PIC_VTYPE_NIL:
     return PIC_TT_NIL;
+  case PIC_VTYPE_TRUE:
+  case PIC_VTYPE_FALSE:
+    return PIC_TT_BOOL;
   case PIC_VTYPE_FLOAT:
     return PIC_TT_FLOAT;
   case PIC_VTYPE_UNDEF:
@@ -27,6 +30,36 @@ pic_nil_value()
   return v;
 }
 
+pic_value
+pic_true_value()
+{
+  pic_value v;
+
+  v.type = PIC_VTYPE_TRUE;
+  v.u.data = NULL;
+  return v;
+}
+
+pic_value
+pic_false_value()
+{
+  pic_value v;
+
+  v.type = PIC_VTYPE_FALSE;
+  v.u.data = NULL;
+  return v;
+}
+
+pic_value
+pic_bool_value(bool b)
+{
+  pic_value v;
+
+  v.type = b ? PIC_VTYPE_TRUE : PIC_VTYPE_FALSE;
+  v.u.data = NULL;
+  return v;
+}
+
 pic_value
 pic_obj_value(void *ptr)
 {
diff --git a/src/vm.c b/src/vm.c
index 60bf32c2..c84f9522 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -110,6 +110,12 @@ print_irep(pic_state *pic, struct pic_irep *irep)
     case OP_PUSHNIL:
       puts("OP_PUSHNIL");
       break;
+    case OP_PUSHTRUE:
+      puts("OP_PUSHTRUE");
+      break;
+    case OP_PUSHFALSE:
+      puts("OP_PUSHFALSE");
+      break;
     case OP_PUSHNUM:
       printf("OP_PUSHNUM\t%g\n", irep->code[i].u.f);
       break;
@@ -259,6 +265,16 @@ pic_gen(pic_state *pic, struct pic_irep *irep, pic_value obj, struct pic_env *en
       break;
     }
   }
+  case PIC_TT_BOOL: {
+    if (pic_true_p(obj)) {
+      irep->code[irep->clen].insn = OP_PUSHTRUE;
+    }
+    else {
+      irep->code[irep->clen].insn = OP_PUSHFALSE;
+    }
+    irep->clen++;
+    break;
+  }
   case PIC_TT_FLOAT: {
     irep->code[irep->clen].insn = OP_PUSHNUM;
     irep->code[irep->clen].u.f = pic_float(obj);
@@ -380,6 +396,14 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
       PUSH(pic_nil_value());
       NEXT;
     }
+    CASE(OP_PUSHTRUE) {
+      PUSH(pic_true_value());
+      NEXT;
+    }
+    CASE(OP_PUSHFALSE) {
+      PUSH(pic_false_value());
+      NEXT;
+    }
     CASE(OP_PUSHNUM) {
       PUSH(pic_float_value(pc->u.f));
       NEXT;