Erythromycin estolate (EE) in concentration as low as 5 × 10–6M led to the leakage of enzymes from Chang liver cells exposed to the drug. Two other erythromycin derivatives (propionate and base), which differ from EE in that they do not produce hepatic injury in patients, did not lead to leakage of enzyme from the Chang cells until concentrations of these two derivatives reached 5 × 10–4M.