Although everybody is at some risk of developing cancer, individuals whose families show certain characteristics might be at high risk. The existence of families with hereditary cancers have been known for a long time. Meanwhile several genes for these dispositions have been identified, which gives high-risk individuals the opportunity to choose presymptomatic testing. This leads to a new group of "patients", the healthy gene carriers. Genetic counselling is a process which includes verification of diagnosis, pedigree analysis, individual risk assessment, explanation of complex medical and genetic facts and the choice of possible options to deal with the genetic burden (e.g. coping strategies, prevention). Presently cancer gene testing has 2 clinical applications. In affected individuals it is part of the diagnostic procedure, in at risk individuals it segregates gene carriers from non-carriers. With regard to the healthy carriers of highly penetrant mutated genes and to some extend also with regard to the non-carriers this means new medical, psychological, social and ethical tasks. Genetic counselling should be offered to any family with a history of cancer or cancer-linked conditions. It has to be considered that not only patients and their families are laymen with regard to medicine, but that we all are laymen with regard to the leading a life with the knowledge of once own deleterious heritage.