This study explores the problems and uncertainties of older men, with prostate cancer, who have undergone watchful waiting and the strategies they use to manage their concerns. With life expectancy rising, the number of older men with prostate cancer has increased. Nearly 50% of all new prostate cancers are diagnosed in men over 70 years old. For many of these older men, improvements in medical care have increased the likelihood of living for years with prostate cancer. Thus, watchful waiting has been proposed as a reasonable alternative to treatment for older men with localized prostate cancer. A qualitative, descriptive design was used for this study. The results from interviews with 10 men who were undergoing watchful waiting for prostate cancer were analysed using the Mishel's Reconceptualized Uncertainty in Illness model. Domains of uncertainty, appraisal of danger and appraisal of opportunity were identified and each was supported by participant's experience. The results of the study may be used to expand the Uncertainty in Illness model and develop interventions for men undergoing watchful waiting for prostate cancer. These findings may be used to enhance current nursing interventions for men electing for watchful waiting as an alternative to treatment for prostate cancer, including patient teaching and support services. Future study should examine the role of nurses in managing uncertainty, especially in patient teaching and in the development, implementation and evaluation of interventions to manage uncertainty.