Thirty children with simple febrile convulsions were treated with sodium valproate following their second convulsion. Twenty-two of the 30 (73%) had no further convulsions during the one-year period of observation compared with 17 of 28 in the control group (61%). This was not a statistically significant difference. Side effects attributed to sodium valproate treatment were noted in 7 patients (23%), although 4 of these showed only mild transient gastrointestinal symptoms at high dosage. The study did not confirm any advantage in the use of sodium valproate as a prophylaxis for febrile convulsions, although compliance was good and significant side effects infrequent.