Objective To discuss the clinicopathologic features, diagnosis and treatment of pri-mary prostatic signet ring cell carcinoma (PPSRCC). Methods Clinical data of 23 PPSRCC cases were retrospectively reviewed. The mean age was 74 years and majority of them had aggravated dysu-ria. The mean serum PSA was 45.3 ng/ml (7.4-126.8 ng/ml). To exclude the metastasis from stomach and colon SRCC, upper gastric tract endoscopy and barium enema were carried out. Seven pa-tients received radical prostatectomies and 2 patients who had positive margins received hormonal and radiation therapy. The rest of patients received maximal androgen blockade therapy. Photoselective vaporization of the prostate was performed on 11 patients who had lower urinary tract symptoms. All cases were investigated by routine pathological, immunohistochemical studies. Results Seventeen cases of PPSRCC were associated with concurrent high-grade prostatic carcinoma, only 6 cases were pure SRCC. Immunohistochemical stains were positive in all cases for PSA and PAP. Stains were ne-gative for AB/PAS (23/23) and CEA (21/23). The clinical TNM stages were 7 of Ⅱ , 10 of Ⅲ and 6 of Ⅳ. Follow-up was available on 20 cases with a mean 24 months and 3 cases were lost during follow up. Eight cases died of metastasis. Five cases had evidence of recurrence 12-21 months from presen-tation. Conclusions The diagnosis of PPSRCC depends on pathological and immunohistochemical studys after metastasis from stomach and colon SRCC is excluded. Early diagnosis and combination treatment for PPSRCC might improve its prognosis.