The categories of medical condition which have most often been responsible for permanent disqualification of flying personnel have not been previously well documented. In this study, 304 USAF rated personnel were identified from the USAF Medical Waiver File. These pilots and navigators were grounded during 1980 and 1981 and have not been returned to flying duties after 1-2 years of follow-up. The disqualifying conditions were reviewed, listed individually, and grouped by major disease categories. Age factors related to these conditions were examined. Cardiovascular disease, as a category, was found to be the commonest cause (30%) of disqualification in this group. Other internal medical and neurological diseases are frequent reasons for permanent disqualification.