Life-threatening health events prompt psychological distress that may motivate individuals to reduce health risks. If so, interventions timed to take advantage of these 'teachable moments' could be particularly effective. To explore this association, early stage prostate and breast cancer patients were identified from a hospital-based tumor registry within 6 years of diagnosis. These patients (n = 920) completed a mailed survey assessing the Horowitz impact of events scale, risk behaviors and readiness to change the behaviors. Breast cancer patients, younger patients and those reporting poor health status reported the greatest impact of the cancer diagnosis. Impact was inversely associated with time from diagnosis for prostate, but not breast cancer patients. Prostate patients who reported exercising regularly had lower impact scores than those who were not exercising (medians: 0.13 vs 0.56, respectively; p = 0.02). Breast patients who were eating five or more fruits and vegetables reported lower impact scores than those who were not eating the recommended servings (0.75 vs 1.06, respectively; p = 0.03). Breast patients who were non-smokers reported lower impact scores than smokers (0.88 vs 1.31, respectively; p = 0.02). Prospective studies are needed to understand the psychological impact of cancer diagnosis and how it might facilitate or impede the adoption of health promoting behaviors. Copyright (C) 2000 John Wiley and Sons, Ltd.