We review current knowledge and application of genetic counselling for psychiatric disorders. Empirical data for genetic counselling exist for affective disorder, schizophrenia, Alzheimer's and Huntington's disease. In Huntington's chorea and partly in Alzheimer's disease molecular genetic methodology may be applied, whereas for affective disorder and schizophrenia only empirical risk figures are available. We describe the principles of genetic counselling and their application in the respective diseases. Problems of presymptomatic testing are particularly outlined. In addition, teratogenic aspects of therapy with psychopharmacological agents during pregnancy are discussed.