Serum transaminase levels (serum glutamic-oxaloacetic transaminase or serum glutamic-pyruvic transaminase) were found to be altered in 40 (21.39%) of 187 patients with oral lichen planus. The patients with oral lichen planus who had altered transaminase levels were on average older than those without liver disorders and exhibited a higher percentage of erosive lesions (p < 0.05) and tongue involvement. Histologically, no statistically significant differences were noted in the extension of inflammatory infiltration or in connective tissue density; nevertheless, the latter was greater in patients without altered transaminase levels. Finally, among those patients with altered liver test results and erosive lichen planus, serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase levels were found to be higher than levels in those patients without erosions. This indicates that behavior of the oral lesions is more aggressive as the degree of liver alteration increases. We emphasize that of the 40 patients with altered transaminase levels (all later proved to reflect chronic hepatitis through complementary diagnostic methods), 28 had hepatitis C virus infection.