Common carp is one of the leading species in world aquaculture, but selective breeding for growth rate has not been actively pursued in this species after unsuccessful selection experiments. We estimated heritability for growth-related traits at 8 weeks of age in Hungarian Synthetic Mirror carp at Vodnany (Czech Republic). Parentage assignment with eight microsatellite markers was used in a full factorial cross of 10 dams  24 sires. Out of 550 offspring, 95.3% could be assigned to a single parental pair. Animal model heritability estimates were 0.33 F 0.08 for weight 0.33 F 0.07 for length and 0.37 F 0.07 for Fulton's condition factor (K). Maternal effects and dominance were not significantly different from zero. The genetic correlation between weight and length was 0.98, and negative correlations were found between K and length (À 0.38) and K and weight (À 0.17). It is concluded that selective breeding for increased weight gain can be successful in juvenile carp, using indirect selection for length. However, the facts that heritability was estimated at 8 weeks of age and not at harvest weight, as well as a possible amplification of additive variance by competition, are limitations to the applicability of the present results.