A digital television transmitting system includes a frame encoder, a block processor, a group formatter, and a multiplexer. The frame encoder forms an enhanced data frame and encodes the data frame for error correction and for error detection. The block processor further encodes the encoded data frame at a rate of 1/2 or 1/4, and the group formatter divides the encoded data frame into a plurality of enhanced data blocks and maps the divided data blocks into a plurality of enhanced data groups, respectively. The multiplexer multiplexes the enhanced data groups with main data.