Little is known about the natural course of arachnoidal cysts (AC) and the incidence of complications. This poses a problem in selection of patients for surgical interventions. The present authors report on 19 children with supratentorial AC of varying location and size. The mean follow-up time is 6 years. The evolution of presenting symptoms, the developmental course, the occurrence of complications, the surgical intervention performed and its outcome are described. Associated neurological disorders cannot always be attributed to the cyst. If surgery is being considered, a causal relationship between the symptom and the cyst should be plausible.