The long-term (1) effect of multiple insulin injections in clinical practice was evaluated prospectively in 168 unselected consecutive insulin-dependent diabetic patients, age 31 (10-77) yr, attending a diabetic clinic. All patients received three or more daily injections of short acting insulin using a pen injector (NovoPen) plus one injection of intermediate acting insulin at bedtime. Haemoglobin A1c remained nearly unchanged, baseline: 8.6 (5.7-11.8)%, and after intensified treatment for 12 months: 8.3 (5.7-12.3)%. The frequency of keto-acidosis (0.08 (conventional treatment) versus 0.02 episodes/patient/yr, p less than 0.05) and severe hypoglycaemia (0.69 (conventional treatment) versus 0.38 episodes/patient/yr, p less than 0.005) diminished during intensified treatment. Ninety percent of the patients reported improvement in general well-being and only three percent felt worse. We conclude that multiple insulin injections with a pen injector applied in clinical practice improves general well-being, diminishes the risk of acute metabolic complications, while the overall metabolic control as reflected by haemoglobin A1c remains unaltered.