Regular exercise has long been known as an adjunct in the therapy of diabetes mellitus. There are, however, only few reports on the impact of this therapy during pregnancy. This study aims at presenting an exercise programme for patients with insulin-requiring gestational diabetes (GDM) and its short-term and long-term effects on carbohydrate metabolism, on the foetus and on the course of pregnancy. Between the 26th and 32nd week of gestation, 41 pregnant subjects were randomised into either an exercise and diet group (EXE) or an Insulin and diet group (INS). The EXE patients (N = 21) trained three times per week at 50% VO2max. For 3 x 15 minutes on a recumbent bicycle ergometer throughout pregnancy with blood glucose monitoring before and after exercise). Blood glucose metabolism was followed by daily home monitoring and weekly fasting blood glucose sampling (FBG). The FBG results were comparable in the study and the control group (105 mg/dl); the maternal and foetal complications did not differ significantly between the two groups. The glycaemic parameters indicate a persistent decrease in blood glucose and an increase in insulin sensitivity induced by regular physical activity. We conclude, that such a medically supervised exercise programme can be safely conducted in women with GDM resulting in normoglycaemia for the mother and thus preventing insulin therapy.