The bioavailability and absorption pattern of theophylline from a single dose of a slow release theophylline sprinkle product (Somophyllin) were investigated in 10 asthmatic children both in fasting conditions and after a standardized breakfast. Theophylline given intravenously was used as a reference. The fasting absorption of Somophyllin was rather fast with peak serum theophylline levels 3-5 h (mean 3.7 h) after dosing. Food produced a small but statistically significant reduction in the rate of absorption of theophylline, so that the mean time to peak serum theophylline level was 5.6 h (range 4-8 h) after food. In no case was there any important difference between the absorption profiles on the test days, and the bioavailability was complete after both fasted and fed intake of the product (92.5% and 105%, respectively). It is suggested that to obtain the optimum absorption profile children should take Somophyllin with food rather than between meals.