The age and sex distributions of GP consultations and emergency hospital admissions for pneumothorax are shown here. In males there is a marked increase in early adult life which peaks in the 20's and then falls until the 40's when it increases again. In females, the incidence is lower than in males but there is a similar tendency for a rise and fall in early adult life followed by an increase after the 50's. The younger age group (15-34 years) accounts for nearly half of cases with incidences in general practice of 37 per 100,000 per year for males and 15 per 100,000 per year for females and for hospital admissions, 26 and 9 per 100,000 per year respectively. The older age group (55+ years) accounts for about third of cases, with male and female incidence rates in general practice of 33 and 11 per 100,000 per year respectively, while equivalent figures for hospital admissions are 25 and 6 per 100,000 per year respectively.