Clinical trials of lamotrigine (LTG) began in 1984. By November 1992 about 5,800 patient-years' experience of adverse effects had been compiled. In general, LTG has an acceptable safety profile. Mild central nervous system adverse effects such as ataxia, dizziness, and headache occur significantly more frequently with LTG than with placebo but seldom demand discontinuation of LTG therapy. Dosage-related allergic skin rash occurs in about 5% of patients. The rash rarely is severe enough to require hospitalization. The adverse-reaction profile of LTG compares favorably with that of traditional antiepileptic drugs.