Previously reported figures for the incidence of Adult Respiratory Distress Syndrome, based largely on American results, would suggest that the average British Health District of 200,000 people could expect to see 130 cases per year. This figure is greatly in excess of that expected from our clinical experience. We have undertaken a retrospective survey of patients within a British Health Region (population, 3,599,400). Results indicate an incidence of nine for an average Health District of 200,000 population, or 2.5% of all admissions to intensive therapy units, or 0.045 per 1000 resident population.