Autoantibodies to a number of epithelial components have previously been described in small groups of patients with lichen planus. Recently a group of antibodies to monkey esophagus have been detected in lichen planus related to hepatitis C virus infection. This study has examined the frequency of serum antiepithelial antibodies in a group of patients with idiopathic oral lichen planus and lichenoid drug reactions. Five of 34 patients with idiopathic lichen planus and two of six patients with lichenoid eruptions had circulating antibodies that gave rise to an antinuclear pattern when examined using epithelial tissue. However, these antibodies were present in only low titer and were not specific to a particular clinical presentation of lichen planus or lichenoid drug reaction. It seems likely therefore that such antibodies do not play an important part in the etiopathogenesis of lichen planus, and their detection is unlikely to be beneficial in the diagnosis of this disease.