The last two decades have witnessed a surge in research investigating the application of oxytocin as a method of enhancing social behaviour in humans. Preliminary evidence suggests oxytocin may have potential as an intervention for autism. We evaluated a 5-day "live-in" intervention using a double-blind randomized control trial. 38 male youths (7-16 years old) with autism spectrum disorders were administered 24 or 12 international units (depending on weight) intranasal placebo or oxytocin once daily over four consecutive days. The oxytocin or placebo was administered during parent-child interaction training sessions. Parent and child behaviours were assessed using parent reports, clinician ratings, and independent observations, at multiple time points to measure side-effects; social interaction skills; repetitive behaviours; emotion recognition and diagnostic status. Compared to placebo, intranasal oxytocin did not significantly improve emotion recognition, social interaction skills, or general behavioral adjustment in male youths with autism spectrum disorders. The results show that the benefits of nasal oxytocin for young individuals with autism spectrum disorders may be more circumscribed than suggested by previous studies, and suggest caution in recommending it as an intervention that is broadly effective.