Comparisons were made between male and female children with autism, 384 boys and 91 girls, aged 3 years to 8 years, on nonverbal measures of intelligence, adaptive functioning, receptive vocabulary, perception, and eye-hand integration, and on ratings of affect, play, and relating and human interest. Males showed more advanced performances on eye-hand integration and perception skills on the Psychoeducational Profile (PEP) and had higher nonverbal IQs social quotients, and Peabody Picture Vocabulary Test (PPVT) IQs than females. When nonverbal IQ was controlled, the main effect of sex remained; however, sex differences on PPVT scores and on eye-hand integration and perception scale disappeared. Males showed more unusual visual responses and less appropriate, more stereotypic play than females. These results are discussed in terms of hypotheses concerning sex differences in genetic thresholds and in hemispheric lateralization.