Thank you, Jan Zizka, Roman Kellner I would expect that the allignment has only influence on the address of variables, not on the total size of a structure. It looks like the compiler calculates the size of the structure to be a multiple of the largest item in the structure. What I want is to allign each variable in the structure to it's own size, but the total size of the structure to be the actual size. Is this possible? Eric ---- struct { unsigned char Value2; unsigned char Value3; unsigned char Value4; } Value; sizeof(Value) = 3; struct { unsigned short Value1; unsigned char Value2; unsigned char Value3; unsigned char Value4; } Value; sizeof(Value) = 6; (not 5) struct { unsigned long Value1; unsigned char Value2; unsigned char Value3; unsigned char Value4; } Value; sizeof(Value) = 8; (not 7)