OBJECTIVE Molecular genetic advances have increased the demand for DNA testing. We describe DNA based genetic counseling in a hereditary nonpolyposis colorectal cancer (HNPCC) family. METHODS This extended HNPCC family was found to harbor the MSH2 germline mutation. Family history, medical, and pathology documents enabled us to secure a high degree of verification that the kindred qualified as HNPCC. DNA testing revealed the MSH2 germline mutation that was verified independently in two laboratories. Genetic counseling was provided before DNA testing and disclosure of MSH2 findings. RESULTS Genetic counseling revealed a variety of findings characterized by emotional stress in MSH2 germline mutation carriers. Concerns centered around reproductive issues, potential transmission of the deleterious gene to their progeny, and discrimination by insurance carriers and employers. More than one-half of the patients found to harbor the MSH2 mutation considered the option of prophylactic subtotal colectomy. CONCLUSIONS DNA testing should be restricted to well-verified candidate families in which genetic counseling should be mandatory. HNPCC family members sought genetic risk assessment for their own health and that of their children. Contrasting emotional responses took place when told of their gene testing status and this required a sensitive empathetic listening ear. Patients have many concerns about their lifetime cancer destiny when told that they harbor the culprit MSH2 germline mutation.