The benefits of early detection screening for prostate cancer are still unclear and current screening guidelines recommend that men make an informed, personal decision based on an understanding of the risks, benefits, and uncertainties associated with screening. Men with a first-degree family history of prostate cancer are at more than double the risk of being diagnosed with prostate cancer than are men without a family history. However, contrary to predictions put forward in previous research, although men with a family history of prostate cancer report greater risk perceptions and prostate cancer screening behaviour, increased risk perceptions do not predict screening. Previous research on how men with a family history of prostate cancer integrate heightened familial risk information into what is already a complex health decision has neglected to examine how men understand, combine, and weigh information about prostate cancer risk and the uncertainties of early detection screening to reach their decisions. The aim of the current thesis was to address these issues by applying three major theoretical models of judgement and decision-making to examine prostate cancer screening decisions for men with a family history and comparing their decisional process with that of men without a family history.