(1) The standard treatment for type 1 diabetes is intensive insulin therapy, consisting of at least 3 daily injections of different insulins, one of which is a long-acting insulin. (2) Insulin detemir is the second long-acting human insulin analogue to be marketed in Europe (after insulin glargine) for the treatment of diabetes in adults and children over 6 years of age. Its action lasts about 12 hours. (3) Insulin detemir was evaluated in around 10 comparative trials, all unblinded, examining the effect of insulin detemir in terms of global glycaemic control (HbA1c level). None of these trials examined whether insulin detemir prevented complications of diabetes. (4) About 10 trials, involving more than 3000 patients, showed that insulin detemir, insulin isophane and insulin glargine have similar efficacy in treating both type 1 and type 2 diabetes. (5) The short-term adverse effect profile of insulin detemir is similar to that of isophane insulin. There is slightly less weight gain with insulin detemir, but injection site reactions occur more frequently. The long-term adverse effects of insulin detemir are not known. (6) Insulin detemir is a clear solution, leading to a risk of confusion with ordinary human insulin or a fast-acting insulin analogue. (7) In practice, isophane insulin remains the first choice long-acting insulin for patients with type 1 or type 2 diabetes.