The purpose of this study is to evaluate a new class of biologic agent, the monoclonal antibody (mAb) drug conjugate SGN-15 (cBR96 - Doxorubicin immunoconjugate), used in combination with the taxane agent, TAXOTERE (docetaxel) as a strategy for targeting advanced stage, hormone refractory prostate carcinoma (HRPC). This is a randomized, open label, phase II study evaluating the immunoconjugate SGN-15 in combination with the taxane TAXOTERE in comparison to TAXOTERE alone in patients with HRPC. Based on a previous phase I study of the SGN-15/TAXOTERE combination, the weekly dose of SGN-15 will be 200 mg/m2 and the weekly dose of TAXOTERE will be 35 mg/m2. The schedule of administration for both agents will be weekly, with SGN-15 administered prior to the TAXOTERE in the patients treated with the combination. A single course of therapy will be defined as 6 weekly doses followed by a 2 week rest period for a total of 8 weeks. The study will perform an interim analysis of the data after 80 patients have completed two courses. Patients should be treated for a minimum of 2 courses of therapy. Additionally, for patients who remain eligible and have experienced tolerable levels of drug toxicity, repeat dosing with subsequent cycles is possible. Patients will be removed from study if there is evidence of tumor progression or intolerable toxicity. Follow-up assessments include adverse event reporting, clinical laboratory studies, and quality of life (QOL) assessment using a validated QOL instrument.