The Multiphasic Health Checkup Evaluation Study, a long-term clinical trial, has been completed. A study group of 5156 men and women age 35-54 at entry was urged to have annual multiphasic health checkups (MHCs) for 16 years. A control group of 5557 comparable subjects was not so urged but was followed up in a comparable fashion. The mean and median number of MHCs per person were 6.8 and 6, respectively, in the study group and 2.8 and 1, respectively, in the control group. During 16 years the study group experienced a 30% reduction (p less than 0.05) in deaths from pre-specified ‘potentially postponable’ causes, largely associated with lower death rates from colorectal cancer and hypertension. This reduction was most pronounced in the early years of the study. The two groups did not differ to a statistically significant degree in mortality from all other causes (84% of total mortality) or in total mortality. There was no difference in self-reported disability in the overall groups. In the setting of our prepaid health care plan where MHCs were already available on a voluntary basis, a program of urging middle-aged persons to undergo regular MHCs brought about a substantial reduction in mortality from preselected diseases.