Methods: Four studies were conducted: Study A, was a pilot study which examined fatigue over 3 months after different treatments for localised prostate cancer (radiotherapy, brachytherapy and androgen deprivation, n=45). Study B focussed on fatigue over 12 months after brachytherapy (n=51). Two cross sectional postal surveys explored fatigue in recurrence free prostate cancer survivors (Study C, n=443) and hormone controlled prostate cancer (Study D, n=198). Throughout, fatigue was assessed using the Brief Fatigue Inventory and a case definition of clinically significant fatigue (CSF) was also constructed and applied in Studies A and B. Results: Study A found CSF increased after treatment but returned to baseline 3 months after radiotherapy, whereas it appeared to be prolonged after brachytherapy. CSF was not associated with C reactive protein or interleukin-6. Study B found CSF increased between baseline and 1 month after brachytherapy (6 vs.29%, p=0.001) and was higher than the non-cancer comparison group (29 vs. 4% p=0.001). CSF returned towards baseline levels of 6 months. There were no baseline predictors of developing CSF. Study C found 29% of recurrence free prostate cancer survivors had fatigue after radiotherapy or radical prostatectomy (33 vs. 22% p=0.024) but it was not independently associated with treatment received after controlling for other factors 43% of men with hormone controlled prostate cancer had fatigue in Study D. Conclusions: Fatigue is an important symptom in men treated for prostate cancer but resolves within months of brachytherapy. Almost one third of recurrence free survivors have fatigue but it does not appear to be related to the type of treatment received. Fatigue is most prevalent in men with hormone controlled prostate cancer.