diff --git a/doc/ca65.sgml b/doc/ca65.sgml
index 19c09b85d..278a81d1b 100644
--- a/doc/ca65.sgml
+++ b/doc/ca65.sgml
@@ -1191,6 +1191,35 @@ writable.
   assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
 
 
+<sect1><tt>.ASIZE</tt><label id=".ASIZE"><p>
+
+  Reading this pseudo variable will return the current size of the
+  Accumulator in bits.
+
+  For the 65816 instruction set .ASIZE will return either 8 or 16, depending
+  on the current size of the operand in immediate accu addressing mode.
+
+  For all other CPU instruction sets, .ASIZE will always return 8.
+
+  Example:
+
+  <tscreen><verb>
+	; Reverse Subtract with Accumulator
+	; A = memory - A
+	.macro rsb param
+		.if .asize = 8
+			eor	#$ff
+		.else
+			eor	#$ffff
+		.endif
+		sec
+		adc	param
+	.endmacro
+  </verb></tscreen>
+
+  See also: <tt><ref id=".ISIZE" name=".ISIZE"></tt>
+
+
 <sect1><tt>.CPU</tt><label id=".CPU"><p>
 
   Reading this pseudo variable will give a constant integer value that
@@ -1218,6 +1247,19 @@ writable.
   </verb></tscreen>
 
 
+<sect1><tt>.ISIZE</tt><label id=".ISIZE"><p>
+
+  Reading this pseudo variable will return the current size of the Index
+  register in bits.
+
+  For the 65816 instruction set .ISIZE will return either 8 or 16, depending
+  on the current size of the operand in immediate index addressing mode.
+
+  For all other CPU instruction sets, .ISIZE will always return 8.
+
+  See also: <tt><ref id=".ASIZE" name=".ASIZE"></tt>
+
+
 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
 
   This builtin pseudo variable is only available in macros. It is replaced by
diff --git a/src/ca65/expr.c b/src/ca65/expr.c
index 0352b3c80..307772a5a 100644
--- a/src/ca65/expr.c
+++ b/src/ca65/expr.c
@@ -1099,6 +1099,15 @@ static ExprNode* Factor (void)
             N = Function (FuncAddrSize);
             break;
 
+	case TOK_ASIZE:
+            if (GetCPU() != CPU_65816) {
+                N = GenLiteralExpr (8);
+            } else {
+	        N = GenLiteralExpr (ExtBytes [AM65I_IMM_ACCU] * 8);
+            }
+	    NextTok ();
+	    break;
+
         case TOK_BLANK:
             N = Function (FuncBlank);
             break;
@@ -1132,6 +1141,15 @@ static ExprNode* Factor (void)
             N = Function (FuncIsMnemonic);
             break;
 
+	case TOK_ISIZE:
+            if (GetCPU() != CPU_65816) {
+                N = GenLiteralExpr (8);
+            } else {
+                N = GenLiteralExpr (ExtBytes [AM65I_IMM_INDEX] * 8);
+            }
+            NextTok ();
+	    break;
+
         case TOK_LOBYTE:
             N = Function (FuncLoByte);
             break;
diff --git a/src/ca65/pseudo.c b/src/ca65/pseudo.c
index 4484e3c26..4db780318 100644
--- a/src/ca65/pseudo.c
+++ b/src/ca65/pseudo.c
@@ -1967,6 +1967,7 @@ static CtrlDesc CtrlCmdTab [] = {
     { ccNone,           DoUnexpected    },      /* .ADDRSIZE */
     { ccNone,           DoAlign         },
     { ccNone,           DoASCIIZ        },
+    { ccNone,           DoUnexpected    },      /* .ASIZE */
     { ccNone,           DoAssert        },
     { ccNone,           DoAutoImport    },
     { ccNone,           DoUnexpected    },      /* .BANK */
@@ -2041,6 +2042,7 @@ static CtrlDesc CtrlCmdTab [] = {
     { ccNone,           DoIncBin        },
     { ccNone,           DoInclude       },
     { ccNone,           DoInterruptor   },
+    { ccNone,           DoUnexpected    },      /* .ISIZE */
     { ccNone,           DoUnexpected    },      /* .ISMNEMONIC */
     { ccNone,           DoInvalid       },      /* .LEFT */
     { ccNone,           DoLineCont      },
diff --git a/src/ca65/scanner.c b/src/ca65/scanner.c
index aaba56764..799321066 100644
--- a/src/ca65/scanner.c
+++ b/src/ca65/scanner.c
@@ -139,6 +139,7 @@ struct DotKeyword {
     { ".ALIGN",         TOK_ALIGN               },
     { ".AND",           TOK_BOOLAND             },
     { ".ASCIIZ",        TOK_ASCIIZ              },
+    { ".ASIZE",         TOK_ASIZE               },
     { ".ASSERT",        TOK_ASSERT              },
     { ".AUTOIMPORT",    TOK_AUTOIMPORT          },
     { ".BANK",          TOK_BANK                },
@@ -224,6 +225,7 @@ struct DotKeyword {
     { ".INCBIN",        TOK_INCBIN              },
     { ".INCLUDE",       TOK_INCLUDE             },
     { ".INTERRUPTOR",   TOK_INTERRUPTOR         },
+    { ".ISIZE",         TOK_ISIZE               },
     { ".ISMNEM",        TOK_ISMNEMONIC          },
     { ".ISMNEMONIC",    TOK_ISMNEMONIC          },
     { ".LEFT",          TOK_LEFT                },
diff --git a/src/ca65/token.h b/src/ca65/token.h
index b0264f154..bfc013a3d 100644
--- a/src/ca65/token.h
+++ b/src/ca65/token.h
@@ -126,6 +126,7 @@ typedef enum token_t {
     TOK_ADDRSIZE,
     TOK_ALIGN,
     TOK_ASCIIZ,
+    TOK_ASIZE,
     TOK_ASSERT,
     TOK_AUTOIMPORT,
     TOK_BANK,
@@ -200,6 +201,7 @@ typedef enum token_t {
     TOK_INCBIN,
     TOK_INCLUDE,
     TOK_INTERRUPTOR,
+    TOK_ISIZE,
     TOK_ISMNEMONIC,
     TOK_LEFT,
     TOK_LINECONT,