Recurrent erythema multiforme is an uncommon disorder. We have reviewed the clinical features and treatment of 65 patients with this condition. The mean number of attacks per year was six (range 2-24), and the mean duration of the disease was 9.5 years (range 2-36) reflecting its chronicity. The majority of patients had oral mucous membrane involvement (69%). In 46 patients (71%) the condition was precipitated by a preceding herpes simplex virus infection. Acyclovir was found to be the most useful first-line treatment, with 55% of patients deriving benefit from either continuous oral acyclovir or a patient-initiated 5-day oral course at the onset of herpes simplex virus infection. Of those failing to respond to acyclovir, a small proportion responded to dapsone. The most resistant patients (11) were treated with azathioprine, with complete disease suppression in all cases.