After primary treatment for clinically localized prostate cancer, biochemical recurrence is usually the first evidence of either local recurrence or metastatic progression. This poses a diagnostic dilemma for both the patient and the physician regarding future therapy. Prostate-specific antigen doubling time (PSADT) is a useful tool in this clinical setting. There have been multiple reports of the utility of PSADT in men with isolated biochemical recurrence after either radical prostatectomy or external-beam radiation therapy. Early observations of PSADT in men with recurrence are reviewed and the current literature is summarized to allow physicians to make an accurate assessment of a patient's risk of progression after isolated biochemical recurrence.