A serum concentration profile study on midazolam in children was done. Fifty six children aged 3-10 years took part. The routes investigated were intravenous, intramuscular, rectal and oral at 0.15 mg.kg-1, and the oral at 0.45 mg.kg-1 and 1 mg.kg-1. Serum concentration levels for 5 h were studied using gas liquid chromatography. The volume of distribution, Vss, was 1.29 l.kg-1, the elimination half-life 1.17 h and the serum clearance 9.11 ml.kg-1.min-1. Peak serum concentrations for the intramuscular, rectal and oral routes were at 15 min, 30 min and 53 min respectively. Bioavailability was 87%, 18%, 27% respectively at a dose of 0.15 mg.kg-1. The oral route bioavailability halved to 15% at the two higher doses. Bioequivalence was present between the 0.15 mg.kg-1 intramuscular dose and the 0.45 mg.kg-1 oral dose from 45 to 120 min.