Presymptomatic DNA-testing for Huntington's disease has made it possible to predict whether or not at-risk individuals are gene-carriers with a reliability of about 98%. In our retrospective study of 18 tested individuals, most of the newly identified carriers function apparently well. They use avoidance and repression of affect as psychological defense strategies. However, 8 out of 9 non-carriers do not experience the expected relief about their test results. They experience survivor guilt and emotional numbness and find it difficult to cope with the effects of the test results on the family system. The partners of gene-carriers are at risk of becoming emotionally isolated by putting aside their own feelings for fear of seeming self-centered. Appreciation of these effects on tested individuals is important and professional support is needed to prevent post-traumatic stress disorders. Whatever the test result may be, the working through process may take years rather than months. These findings have important implications for patient care and necessitate an extended period of observation after presymptomatic testing.