Background: There is a growing interest in using cognitive behavioural therapy with people who have Asperger Syndrome and comorbid mental health problems. Aims: To examine whether modified group CBT for clinically significant anxiety in an AS population is feasible and likely to be efficacious. Method: Using a randomised assessor-blind trial, 52 individuals with AS were randomised into a treatment arm or a waiting-list control arm. After 24 weeks, those in the waiting-list control arm received treatment, while those initially randomised to (...) treatment were followed-up for 24 weeks. Results: The conversion rate for this trial was high, while attrition was 13%. After 24 weeks, there was no significant difference between those randomised to the treatment arm compared to those randomised to the waiting-list control arm on the primary outcome measure, the Hamilton Rating Scale for Anxiety. Conclusions: Trials of psychological therapies with this population are feasible. Larger definitive trials are now needed. Declaration of Interest: None Trial Registration: ISRCTN 30265294, UKCRN 8370. (shrink)