The prevalence of autism spectrum disorder (ASD) has increased considerably in the past decades. The primary care paediatrician plays an important role not only in the early recognition of ASD but also in its chronic management. Paediatricians need to be comfortable with the global care of children with ASD. The diagnostic assessment of children with ASD comprises the medical investigations to identify associated or underlying medical conditions. The most important associated conditions are seizures, feeding and gastrointestinal problems, sleep disturbances and dental abnormalities. The care of ASD patients is very demanding since along with the purely medical issues there are challenging behavioural and psychiatric conditions that need consideration and professional skills.