We assessed the effects of sodium valproate and carbamazepine monotherapy on bone mineral density (BMD) in children. BMD at the lumbar vertebrae (L-1-L-4) and radius-ulna was measured by the dual-energy x-ray absorptiometry (DEXA) method in 19 children (9 girls, 10 boys) with uncomplicated epilepsy and in 57 healthy children (28 girls, 29 boys), between the ages of 6 and 12 years. The study patients had been receiving either sodium valproate (n = 13) or carbamazepine (n = 6) monotherapy for more than 6 months. There were no significant differences between the control and study patients in age, height, weight, physical activity, or of serum concentrations of calcium, phosphate, and transaminases (aspartate aminotransferase, alanine aminotransferase). However, the serum alkaline phosphatase concentration was greater in the patient group as compared with the control group. BMD values were lower in girl patients (L-1-L-4; 0.497 +/- 0.08 vs 0.566 +/- 0.07 g/cm(2), p < 0.05), but not in boys (0.534 +/- 0.06 vs 0.530 +/- 0.08 g/cm(2)). While BMD reduction was 8% in valproate therapy (midregion of radius-ulna; 0.287 +/- 0.03 vs 0.312 +/- 0.04 g/cm(2), p < 0.04), it was reduced only 4.5% in the carbamazepine-treated group (0.298 +/- 0.01 vs 0.312 +/- 0.04 g/cm(2), statistically not significant), although the mean durations of monotherapy with valproate (1.8 +/- 0.7 years) and carbamazepine (1.7 +/- 0.8 years) were similar. Thus decreased bone mineralization was observed in children with epilepsy, treated with sodium valproate even though treatment was for a rather short time.