"Field (clinical) trials are indispensable. They will continue to be an ordeal. They lack glamour, they strain our resources and our patience, and they protract the moment of truth to excruciating limits. Still, they are among the most challenging tests of our skills.... If, in major medical dilemmas the alternative is to pay the cost of perpetual uncertainty, have we really any choice?"1
The clinical trial of the effect of hypoglycemic agents on the vascular complications of diabetes mellitus conducted by the University Group Program (UGDP) for the past ten years bears witness to the truthfulness of the above quotation.
The hypothesis that control of the blood glucose level prevents or delays the vascular complications of diabetes has been supported so far only by evidence which is largely conjectural.2 Such a relationship can be documented only with prospective study of patients randomly assigned to treatment regimens that differ