Several cost-utility studies have shown little or no benefit for the cost of screening or treatment of asymptomatic prostate cancer. An important factor in these decision analyses was subject preference/utility. Preference can be defined as a subject s contemplative first choice among a series of alternatives. Utility is derived from the individual preferences for a condition or health state. Preferences are summed and the ensuing value is used to weight survival or other health outcome. OBJECTIVE: This study aimed to: 1) assess preferences for radiotherapy, surgery, hormones, and observation for the treatment of prostate cancer. METHODS: Fifty men, 25 with and 25 without prostate cancer, were interviewed, using the Time Trade-Off (TTO) Technique. RESULTS: The men in this study, regardless of group (cancer vs. no cancer), showed an increased preference for surgery versus radiotherapy or hormones, as compared to observation. This presented logical inconsistencies, since surgery was presented with twice the risk of impotence and three times the risk of incontinence as radiotherapy. The validity of the TTO was therefore assessed by comparing predicted to actual individual utility scores. For example, the utility (U) a man placed on an 80% chance of impotence (IP80) should be half the utility placed on a 40% chance of impotence (IP40), if men attended to probabilities of risk. The observed mean IP80 utility was 0.7957 versus 0.6098 for the predicted (p = 0.0002). Similar differences were found between predicted and observed utility values for other probabilities of impotence and incontinence. CONCLUSION: Threats to the validity of the TTO have been documented. Imperfect as the TTO is, it does provide a more objective process to the traditionally subjective means by which decisions regarding health care policy have been made. Therefore, the TTO requires further testing and modifications to improve validity, some of which are discussed in this presentation.