Rationale: The long-term outcome of idiopathic macrocephaly is presently unknown. Methods and results: In the current study (n=15), MRI conducted at long-term review showed regression of orbito-frontal extradural collections and normal or slightly enlarged ventricular space compared to infant examination. Head circumference had normalised in all but one participant. Neuropsychological assessments of nine participants showed general intellectual ability within the normal range in the majority of participants; however, specific deficits in attention were evident. Clinical interviews conducted with a smaller sub-group revealed anecdotal histories of behavioural difficulties and reading or arithmetic difficulties in half of the total sample. Conclusions: Prospective review studies such as this indicate that abnormal radiological findings in infancy are not necessarily predictive of neurodevelopmental problems and may reflect a normal variant. However, while overall intellectual ability may be within average limits in this diagnostic sample, considerable individual variations remain in specific areas of neuropsychological function.