Seventy-eight non-randomized patients with IDDM, aged 33.8 +/- 9.6 years (mean +/- S.D.), with a duration of diabetes of 16.6 +/- 9.5 years and a HbA1c level of 8.0% +/- 1.5 at baseline were included in the study. The effects of a change from a 3-dose insulin regimen using conventional syringes to a treatment mode using 4 injections per day with a pen injector on metabolic control, perceived distress from diabetes on everyday life and correspondence between expectations and experiences of treatment during a 1-year trial were assessed. The experience measures were registered at baseline and after 3 and 12 months, respectively. HbA1c levels were measured every 3 months. Neither the metabolic control nor the body mass index or rate of hypoglycemic episodes changed during the study period. However, the patients experienced a decreased distress from diabetes, which appeared during the first 3 months and remained unchanged thereafter. The expectations of advantages from the intensified insulin therapy were generally high and were mostly either fulfilled or exceeded by experiences. We conclude that multiple insulin injection therapy, under routine treatment conditions, is subjectively preferable to patients and has favourable effects on their quality of life although something more is required in order to also achieve an improvement of metabolic control.