Over the last 2 decades, the prognostic significance of post-irradiation prostate biopsy has been debated. Studies with long-term follow-up have shown a predictive effect with regard to local tumor failure and disease-free survival. More recently collected data involve the use of prostate ultrasound and prostate-specific antigen; the latter appears to be a good prognostic indicator on its own. Currently, the practical usefulness of post-treatment biopsy for clinically undetectable disease remains undefined, since definitive therapy for positive findings cannot be widely applied, carries significant morbidity, and, as yet, is of questionable benefit. Further study is certainly necessary, and it is perhaps under these conditions that this post-therapy procedure should be used.