We prospectively investigated drug-induced headaches (HA) among 60 epileptic patients receiving felbamate (FBM). Twenty patients (33%) experienced HA. HA was pounding in 11 (55%), steady in 9 (45%), moderate or severe in 19 (95%), occurred at least once a week in all patients, and was relieved by nonnarcotic analgesics in 14 (70%). Mean duration on FBM before HA onset was 19 days. HA occurred with higher FBM doses and was relieved in 8 of 13 patients (62%) with FBM dose reduction. FBM was discontinued in most cases because of risks of anemia or hepatitis; not because of HA. Other side effects included insomnia (25%), gastrointestinal symptoms (27%), and agitation or restlessness (23%). HA is a common dose-related complication of FBM, occurs early after initiation of FBM treatment, and is relieved by dose reduction.