OBJECTIVES: The emotional effects of genetic testing for hereditary nonpolyposis colorectal cancer (HNPCC) provided within a counseling program were assessed among 253 individuals.METHODS: Assessments were scheduled at baseline before testing, and again after 6 and 12 months post-test. Negative emotional reactions were evaluated using the Revised Impact of Event Scale and the Center for Epidemiological Studies-Depression Scale. Monitoring coping style was assessed at baseline using the Miller Behavioral Style Scale. RESULTS: Mean reductions were indicated in distress and depression levels within the first 6 months after counseling and testing. High monitors were generally more distressed than low monitors, specifically if they had indeterminate or positive results. CONCLUSIONS: Genetic counseling and testing for HNPCC do not result in long-term distress for most people. Of the variables investigated, only time and coping style have main effects on emotional reactions, and the impacts of mutation status are moderated by coping style. Psychological interventions, aimed to alleviate adverse emotional effects, were suggested for certain participants, i.e. recipients of positive or indeterminate results who are high monitors.