Despite the increasing interest in recent years in prevention and early recognition of asymptomatic disease, an objectively based program for periodic health screening of asymptomatic adults has yet to be proposed for the primary care physician. This is the third in a series of four articles which will critically examine the feasibility of screening procedures for 36 selected diseases. Six basic criteria are adopted as necessary to justify periodic screening. Specific screening recommendations are made for each disease, and a longitudinal screening program for asymptomatic adults will be proposed in the concluding article of this series.