The relation between tumor kinetics and disease progression in patients with hormone-refractory prostate cancer (HRPC) has not been well described. Biochemical recurrence of prostate cancer is characterized by detectable prostate-specific antigen (PSA) levels after treatment and occurs in approximately 30% of patients after therapy for apparent localized disease. An increase in PSA almost always occurs before clinical evidence of disease. The ability to identify early biochemical failure in patients to assess disease aggressiveness and guide changes in treatment needs to be examined. We examined serial PSA data from 249 patients with metastatic disease to assess PSA doubling time (PSADT) in hormone-naive prostate cancer (HNPC) and HRPC states. In a subset of patients, the relation of PSADT to Gleason score and survival was studied. PSADT decreased from 37.5 ± 4.5 weeks to 15.6 ± 1.6 weeks (mean ± SEM) in patients with HNPC versus HRPC. In this small study, PSADT did not correlate with Gleason score, survival from start of hormonal treatment, length of time receiving hormone therapy, or survival in the HRPC state. The decrease in PSADT with disease state may help provide insight into understanding the biology of late-stage disease.