Detailed liver function test analysis is reported for 30 patients with Alzheimer's disease who were treated with tetrahydroaminoacridine. Results show that a benign elevation of aspartate transaminase occurs in up to 50% cases, that the reaction can be a symptomatic one and that clinical hepatitis can occasionally result. Liver function test changes appear dose-dependent and normalize within 2-4 weeks of stopping the drug or of reducing the dose. Women appear more likely to develop hepatotoxicity than men. Rechallenge with THA in patients previously showing abnormalities in liver function shows that some patients are able to tolerate the drug a second time.