We searched the Cochrane Central Register of Controlled Trials to provide an overview of evidence from randomized controlled trials (RCTs) of therapeutic interventions for autism spectrum disorders. From the final survey (529 RCTs), the mean size was 49 participants (standard deviation 50, range 1-479, median 36, mode 40), with a sharp increase in the number of RCTs from 2008. The most frequently evaluated intervention was antipsychotic treatment (n = 44, 3006 participants). The journal with the most RCTs was the Journal of Autism and Developmental Disorders (N = 104). Most trials were small in size, emphasising the need for research groups to collaborate to generate higher quality data with greater applicability to clinical practice.