To elucidate the genetics of sex determination in common carp (Cyprinus carpio) we attempted to produce homozygous YY individuals using androgenetic reproduction techniques. XY sperm donors were selected from a congenic strain with stable 50:50 sex ratios, produced by repeatedly backcrossing male offspring to a female from a homozygous clone. The YY nature of androgenetic males was tested after crossing with females from different genetic backgrounds. One androgenetic male sired all male offspring, indicating viability of the YY genotype in common carp. Androgenetic reproduction of the same male yielded an all male clone. Viability of the CY genotype in common carp is discussed from an evolutionary background.