Gender differences in autism spectrum disorder (ASD) symptoms and associated problem behaviours over development may provide clues regarding why more males than females are diagnosed with ASD. Fifty-six high-functioning children with ASD, and 44 typically developing controls, half of the participants female, were assessed at baseline (aged 7–12 years) and one-year later, collecting measures of autism, attention and anxiety symptoms, school placement and support information. Findings indicated no gender differences in autistic symptoms. Males were more hyperactive and received more integration-aide support in mainstream schools, and females were more socially anxious. Overall, similar gender profiles were present across two time points. Lower hyperactivity levels in females might contribute to their under-identification. Implications are discussed using a biopsychosocial model of gender difference.