Earlier detection of prostate cancer in the past decade has been accompanied by greater reduction in US prostate cancer mortality than that seen with any other cancer. Prostate cancer is usually diagnosed at early stages and is most commonly treated by prostatectomy, radiotherapy, or brachytherapy. For intermediate- and high-risk prostate cancers, randomized clinical trials have shown survival benefit subsequent to prostatectomy or to combined radiation with androgen-suppressive therapy. However, prostatectomy, radiotherapy, and brachytherapy each can lead to distinct adverse effects. Moreover, for the lowest-risk categories of early stage prostate cancer, evidence supporting an intervention is only indirect. New approaches to surveillance of prostate cancer have consequently emerged that do not eschew treatment altogether. Instead “active” surveillance aims to implement definitive intervention effectively for those low-risk cancers that show a propensity for progression as evidenced by histopathological or serological change during the surveillance interval.