Triploid carps (100%) with 150 (3n=150) chromosomes were obtained by crossing improved tetraploid hybrids ( ♀ , 4n=200) of red crucian carp common carp with diploid yellow river carp (♂, 2n=100). Using PCR detection with specific primers, the transgenic triploid carps (positive triploid fish) which accounted for 44.2% and the non-transgenic triploid carps (negative trip-loid fish) were identified from the triploid carps. On tissue sections, the gonads of 24-month-old positive triploid fish were found to be sterile, and were not able to produce mature gametes during the breeding season. Morphologically, both the positive and negative triploid fish were similar. They had a spindle-shaped, laterally compressed, steel grey body with two pairs of bar-bels. Most of the countable and measurable traits of the triploid carps were intermediate between those of the two parents. Over the last 2 years, the positive and negative triploid fish have been raised in the same ponds. The mean body weight of the positive triploid fish was 2.3 times higher than that of the negative triploid fish. The highest body weight of the positive triploid fish was 2.91 times higher than that of the negative triploid fish. Thus, this study produced fast-growing transgenic triploid carps with reduced ecological risk because of their inability to mate and produce progeny.