METHODS Preference (prospective cohort). METHODS 1b. What's known on the subject? and What does the study add? In general the literature suggests that there is a need for improvement in aiding men diagnosed with early prostate cancer in their decision making about treatment options and that our understanding of this process is inadequate. There is limited data analyzing the reasons why these men decide between potentially curative or observational treatments and data evaluating patients' views before and after definitive therapy are scarce. This study begins the process of understanding the reasons underlying a patient's final treatment decision. Being a prospective study, it looks at the thought processes of these men before treatment during the time the decision is made. It also documents how satisfied patients are with their choice after their treatment and whether they would choose the same treatment again. OBJECTIVE To identify the reasons for patients with localised prostate cancer choosing between treatments and the relationship of procedure type to patient satisfaction post-treatment. METHODS 768 men with prostate cancer (stage T1/2, Gleason≤7, PSA<20 ug/L) chose between four treatments: radical prostatectomy, brachytherapy, conformal radiotherapy and active surveillance. Prior to choosing, patients were counselled by a urological surgeon, clinical (radiation) oncologist and uro-oncology specialist nurse. Pre-treatment reasons for choice were recorded. Post-treatment satisfaction was examined via postal questionnaire. RESULTS Of the 768 patients, 305 (40%) chose surgery, 237 (31%) conformal beam radiotherapy, 165 (21%) brachytherapy and 61 (8%) active surveillance. Sixty percent of men who opted for radical prostatectomy were motivated by the need for physical removal of the cancer. Conformal radiotherapy was mainly chosen by patients who feared other treatments (n=63, 27%). Most men chose brachytherapy because it was more convenient for their lifestyle (n=64, 39%). Active surveillance was chosen by patients for more varied reasons. Post-treatment satisfaction was assessed in a subgroup who took part in the QOL aspect of this study. Of the respondents to the questionnaire, 212(87.6%) stated that they were satisfied/extremely satisfied with their choice and 171(92.9%) indicated they would choose the same treatment again. CONCLUSIONS Men with early prostate cancer have clear reasons for making decisions about treatment. Overall, patients were satisfied with the treatment and indicated that despite different reasons for choosing treatment, they would make the same choice again.