The effects of local treatment with highly purified tannic acid (HPTA) on serum transaminase and alkaline phosphatase activity in burn patients were studied, retrospectively. Temporary elevations in the activity of gamma-glutamyl transferase (GGT), aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and alkaline phosphatase (AP) were observed in both HPTA-treated patients and their matched controls. No statistically significant difference was found between the two patient-groups with respect to the mean enzyme activities, calculated as the areas under the curve between 5 and 15 days post-burn (PBD). These results seem to indicate that HPTA does not cause hepatotoxicity, at least when applied to a burned area corresponding to approximately 10% of the total body surface. This is in agreement with the widespread and frequent use of HPTA in the food, cosmetic and pharmaceutical industries.