The developmental test Bayley-III is widely used in clinical and research settings, but there are no published gender-specific norms. The purpose of the present study was to investigate gender differences in Bayley-III scores in a sample of 55 typically developing children assessed repeatedly at ages 4, 7, 10, 13, 24 and 36 months, and to investigate gender differences in the test-taking behavior of the children as measured with the BRS at 36 months. The results of the study demonstrated gender differences at 24 and 36 months for the Cognitive Scale, at 10, 13, 24 and 36 months for the Language Scale and at 36 months for the Motor Scale. On a subtest level, gender differences were found for the Receptive Communication subtest at 13, 24 and 36 months and for the Fine Motor subtest at 7 and 36 months. In all cases where significant gender differences were found, girls achieved higher mean scores than boys. No gender differences were found in the children's test-taking behavior at 36 months on any of the BRS scales, but independently of gender, higher Bayley-III Cognitive and Motor Scale scores were associated with more compliant test-taking behavior.