In phenobarbital-pretreated rats iproniazid produces distinct hepatotoxic symptoms, whereas moclobemide (Ro 11-1163) does not. Iproniazid's hepatotoxic effect is most impressive in histopathology where marked liver necrosis can be seen. Differences between the two compounds are also noted in the body weight development, mortalities and some haematological and blood chemistry parameters. The reversible and specific monoamine oxidase (MAO)-A inhibitor moclobemide, a benzamide, is therefore completely different from the classical irreversible MAO inhibitors of the hydrazine type and, as also confirmed in the clinical studies, does not have any hepatotoxic effect.