Although autism spectrum disorders (ASD) affect more males than females, it is not clear whether neurobehavioural correlates of ASD are equivalent across genders. This study examined gender differences in neurobehavioural functioning in boys and girls with ASD. Participants were males with ASD (n = 10), females with ASD (n = 13), typically developing males (n = 8), and typically developing females (n = 14). Each completed the stop task, a common measure of response inhibition. Females with ASD demonstrated a significant increase in stopping time (indicating poorer inhibition). By contrast, no response inhibition impairments were evident among males with ASD. Females with ASD may have a different neurobehavioural profile, and therefore different clinical needs, when compared with males with ASD.