Intravenous loading dose of phenytoin treatment (ILP) is a useful treatment but may cause serious adverse events. The present study assessed the appropriate use of ILP in Srinagarind Hospital. The authors reviewed all charts that ILP was ordered between January 1st, 2000 and December 31st, 2001, about indication, the infusion rate, and side effects. There were 206 cases treated with ILP Thirty-two cases (15.7%) received inappropriate treatment by ILP The most common indication was primary prophylaxis before brain surgery. There were 7 cases that developed side effects with 5 cases of high blood phenytoin level. These data showed that physicians should consider more carefully the use of ILP.