Continuous subcutaneous insulin infusion (CSII) of 6 months duration was compared with 6 months of multiple insulin injections (MII) using a pen injector (NovoPen) in a prospective cross-over study with 20 young insulin dependent diabetics by evaluating metabolic control, insulin requirements and patient acceptability. Following both intensified regimens (CSII/MII) serum fructosamine declined significantly from 4.1 +/- 0.7 to 3.4 +/- 0.5 mmol/l and 3.6 +/- 0.7 mmol/l respectively (normal range: 2.2 +/- 0.2 mmol/l). When comparing CSII and MII no significant differences could be demonstrated in mean blood glucose (MBG), fasting plasma ketone bodies, fasting plasma free fatty acids (FFA), fasting plasma human growth hormone (HGH), fasting plasma glucagon or serum fructosamine. Mean insulin requirement was 11.4% higher during MII and glucose instability--demonstrated by the M-values and by the frequency of blood glucose values below 4 mmol/l--was significantly (p less than 0.02) higher during the MII treatment. All of the patients reported a better well-being on both treatment regimens and none of them wanted to go back to conventional therapy (CT). In conclusion, on a long-term basis both regimens result in identical metabolic control, but due to physical discomfort during pump treatment, the insulin pen injector was preferred by the majority (80%) of the patients.