Primary signet ring cell adenocarcinoma (SRCC) of the prostate is a rare malignancy. Only 42 cases have have been repeorted in the literature. Here we report a case of 76-year-old man with signet ring cell carcinoma and adenocarcinoma of the prostate. Tumor cells were stained positive for prostate spesific antigen immunohistochemically and histochemically negative for alcian blue and mucin.