A trial was undertaken to ascertain the effect and acceptability of a multiple insulin injection regimen (MII) in patients with insulin-dependent diabetes mellitus using short-acting monocomponent human soluble insulin (Actrapid HM; Novo) for pre-meal bolus injections with the NovoPen injection device (Novo) and long-acting human insulin (Ultratard HM; Novo) at bedtime. Fifty-four patients, all previously on twice-daily short/intermediate-acting human insulin (Monotard HM; Novo) and Actrapid HM, were randomly selected. There was a significant overall improvement in diabetic control over the 12 weeks of the trial, the glycosylated haemoglobin (Hb A1) dropping from a mean of 9.8 +/- 2.2% to 8.6 +/- 1.7% (P less than 0.05). MII, using the NovoPen, was found to be more convenient than conventional insulin administration by 92% of the subjects. It is concluded that the NovoPen is a useful and convenient means of administering pre-meal boluses in an MII regimen, with a very high rate of acceptance by patients of all ages.