ABSTRACT Data on autism are lacking for Libya. We conducted a hospital-based study in the Neurodevelopment Clinic of Al-Khadra Hospital in Tripoli to estimate the prevalence of autistic spectrum disorders in children attending the clinic. All children referred to the clinic between 2005 and 2009 with a diagnosis of speech and language disorders or behavioural difficulties were assessed. There were 38 508 children in total seen during 2005–09, 180 of whom had a history of delayed speech and language and/or behavioural difficulties. Of the 180, 128 children were diagnosed with autistic spectrum disorder: 99 had classical autism, giving the prevalence of about 4 in 1000. The male:female ratio for autistic spectrum disorders was 4:1 and for autism was 4.5:1. The most common age at presentation was 2–5 years (58%) and 56% presented 6–18 months after the onset of symptoms. Physicians should consider autism in the differential diagnosis of any child presenting with a speech and language disorder and/or behavioural difficulties.