One hundred and eight patients who had been taking phenytoin for a year or more, either alone or in combination with other drugs, were examined for gum hypertrophy by three observers independently. Approximately 90% of the patients showed either mild or no gum hypertrophy and severe swelling occurred in only 1%. The observed standards of oral hygiene were extremely poor. A tendency for higher serum phenytoin levels to be associated with greater gum hypertrophy was observed. Because the condition was causing no problems in over 90% of patients, it is considered that gum hypertrophy per se should not deter a physician from using phenytoin in the treatment of epilepsy.