A prospective study was undertaken to assess the type and frequency of adverse side-effects following the use of intravenous phenytoin in children. Twenty-two children received a total of 100 doses over a 10-month period. Six patients (27%) experienced one or more side-effects, including extravasation of the drug, hypotension and cardiac arrhythmia. No patient developed skin necrosis, including the 'purple glove syndrome'. Recovery from all adverse side-effects was spontaneous and complete. It is possible that some or all of these side-effects may have been caused by an excessive rate of infusion of phenytoin or the saline 'flush' following administration of the drug. The overall frequency of side-effects was perhaps less than expected.