Recombinant DNA technology allows the production of insulin analogues with faster absorption rates from subcutaneous tissue as compared to soluble human insulin. The human insulin analogue B10Asp (mono/dimeric) is absorbed twice as fast as soluble human insulin (hexameric). A double blind, randomised crossover study with a 1-month run-in period and two 2-month treatment periods was performed in 21 male insulin-dependent diabetic (IDDM) patients aged 18-40 years in order to compare the metabolic control obtained with equimolar doses of the analogue B10Asp vs soluble human insulin (Actrapid) given as mealtime insulin and intermediate acting isophane insulin (Protaphane) at bedtime. At the end of each 2-month study period, the patients were admitted to the metabolic ward. We found significantly higher plasma insulin/analogue levels after breakfast, lunch and dinner with B10Asp as compared to Actrapid (p < 0.05). The plasma insulin/analogue levels were significantly lower before lunch and dinner with B10Asp as compared to Actrapid (p < 0.05). Also, the plasma insulin/analogue level tended to be lower at bedtime when comparing B10Asp to Actrapid. The 24-h blood glucose profiles showed identical fasting blood glucose, significantly lower blood glucose after breakfast with the analogue (p < 0.05), no differences in blood glucose after lunch and dinner but a significantly higher blood glucose at midnight using the analogue (p < 0.05). The overall 24-h mean blood glucose concentrations, the daily insulin dose, HbA1c, diet, home blood glucose monitoring and frequency of hypoglycaemia were almost identical in the two treatment periods.(ABSTRACT TRUNCATED AT 250 WORDS)