The natural history of isolated congenital pulmonary valve incompetence has been determined by actuarial and parametric techniques from 72 cases collected from the literature. Symptoms developed within 20 years in 6% (CL 4% to 9%) of the patients and within 40 years in 29% (CL 22% to 36%). The hazard function of the development of symptoms demonstrates a risk increasing in time, particularly evident after 40 years. Death followed the appearance of symptoms after an average of 39 months in 3 patients who died. The surgical implications as regards the use of transannular patches and valveless extracardiac conduits are discussed.