Based on these facts, a conference on the Scientific Basis of Respiratory Therapy, co-sponsored by the American Thoracic Society and the Division of Lung Diseases, issued a recommendation to develop a controlled clinical study of IPPB. Contracts were awarded to five clinical centers and a data center in November 1976. Planning of the trial ended in November 1977. Recruitment began in April 1978 for the 985 individuals who took part in this trial and ended in October 1980. Patients enrolled after March 31, 1980, were followed for 30 months instead of 36 months. Follow-up was completed in May 1983.