The purpose of the present study was to examine possible differences between high-functioning males and females with autism spectrum disorder (ASD) regarding the core symptoms of autism and coexisting psychopathology. A total of 23 females and 23 males matched for age, IQ, and ASD diagnoses were recruited(mean age 11y 9mo [SD 4y 5mo], range 5y-20y 2mo) with an IQ above the range of learning disability (mean IQ 88.8 [SD 18.5], range 70-128). They were compared using the Autism Diagnostic Interview-Revised, the Autism Diagnostic Observation Schedule, and the Child Behavior Checklist/4-18. We did not identify striking differences between males and females for the triad of autism core dysfunctions (deficits in reciprocal social interaction, communication, and repetitive, stereotyped behaviours) as assessed by expert ratings. However, with regard to several domains of coexisting psychopathology, parent reports revealed significantly more symptoms in females than males, particularly social problems (t=4.47, p<0.01, d=1.20), attention problems (t=3.39, p<0.01, d=0.80), and thought problems (t=3.24, p<0.01, d=0.84). These results are discussed with possible interpreting bias by parents who may expect more socially desired behaviour from daughters than from sons. The severity of social and attention problems in high-functioning females with autism emphasizes the need for thorough assessments and interventions in these domains. Future research should compare the cognitive phenotype of autism between sexes.