Thirty-three normoglycemic pregnant diabetic patients (White B-R) were studied in the course of one year during 732 weeks of therapy with 176 dose adjustments of insulin to determine patterns of insulin requirements. By means of an empirical formula, the insulin requirements within a 24-hour period can be calculated. Insulin requirement in the course of pregnancy decreases significantly between the tenth and the 16th week of gestation (-12%, P = less than .001). From the 17th to the 36th week it increases slightly at first and more markedly from the 28th week onward (+ 62%), decreasing again from the 36th week onward. Insulin distribution during the day depends on whether or not a residual function of beta cells and, consequently, basal insulin secretion exists. Either four doses of regular insulin are injected or three doses of regular insulin are combined with one to two doses of variously long-acting insulin. The ideal distribution regarding the type and amount of insulin follows certain patterns and can therefore be approximated.