The optimal management strategy for men who have localized prostate cancer remains controversial. This study examines the extent to which suggested treatment based on the perspective of a group or society agrees with that derived from individual patients' preferences. A previously published decision analysis for localized prostate cancer was used to suggest the treatment that maximized quality-adjusted life expectancy. Two treatment recommendations were obtained for each patient: the first (group-level) was derived using the mean utilities of the cohort; the second (individual-level) used his own set of utilities. Group-level utilities misrepresented 25-48% of individuals' preferences depending on the grade of tumor modeled. The best kappa measure achieved between group and individual preferences was 0.11. The average quality-adjusted life years lost due to misrepresentation of preference was as high as 1.7 quality-adjusted life years. Use of aggregated utilities in a group-level decision analysis can ignore the substantial variability at the individual level. Caution is needed when applying a group-level recommendation to the treatment of localized prostate cancer in an individual patient.