'Genetic counselling is the process by which patients or relatives at risk of a disorder that may be hereditary are advised of the consequences of the disorder, the probability of developing and transmitting it and of the ways in which this may be prevented or ameliorated.' The genetic counsellor will discuss the genetic basis and medical facts and also possible personal, familial, social and insurance implications of the respective disorder with the consultand. Further diagnostic investigations, such as genetic tests, may be helpful or necessary for risk predictions or may be required to reach a firm diagnosis. In asymptomatic individuals at risk for a late-onset genetic disorder genetic counselling is obligatory for predictive genetic testing. Genetic counselling also should be offered to symptomatic patients before a diagnostic test is performed. Thereby the patients might become aware in time about the personal, familial and social consequences of the test result that may exceed that of their actual illness. Due to medical confidentiality the geneticist is not allowed to contact other family members and to inform them about a familial disorder and warn them about their own genetic risk. This is the concern of the consultand. Various aspects make up genetic counselling as a specific process which concerns genetic diagnosis, risk estimation and accurate information on medical and genetic facts, but also has a supportive role ensuring that consultands may benefit from given advice and possible preventive measures.