This is a single-arm, open label phase II trial of the investigational agent, Ara-C (cytarabine), in patients diagnosed with hormone refractory prostate cancer whose disease has progressed on or deemed not suitable for standard chemotherapy with docetaxel. Ara-C appears to inhibit DNA synthesis and is cytotoxic to a wide variety of mamalian cells. Recent discoveries have suggested the role of gene fusions in the ETS family of transcription factors as important for the development of prostate cancer. Ara-C appears to block ETS genes, suggesting that it is worthwhile to explore Ara-C as a potential new treatment for patients with hormone refractory prostate cancer given that there is no standard of care for the proposed patient population. In this study, Ara-C will be administered intravenously for 2 days every 3 weeks (1 cycle). Treatment will be for 6 cycles if tolerated and may be continued in patients who are responding and do not have severe toxicity.