In old transcultural psychiatry there was a presupposition that men, all over the world, were equal in their biological quality and that differences in the phenomenology of illnesses were the result of cultural and environmental influences. Now there is an increasing evidence that ethnic groups differ substantially also in their biology. Differences in phamacokinetics and pharmacodynamics cause different responses on drugs. In this article we review some of those differences with respect to the main groups of psychopharmaca.