Prostate carcinoma occurs infrequently in patient less than 50 years old with an incidence of 0.8% to 1.1%. In literature are described less than 20 cases occurred in younger men (< 40 years old). A 36 year-old man with a two-months history of lower back pain, anorexia and loss of weight, showed at clinical examination a mild enlargement of inguinal lymph nodes and right inferior leg and scrotus edema. CT scan demonstrated marked enlargement and fusion of pelvic, inguinal, sacral and periaortic nodes with a pelvic mass that caused local ureterohydronephrosis and obstruction of the urinary flow. X-rays showed osteoblastic metastases. At total body scintigram were observed fixation areas corresponding to lumbar metamers, pelvis, thigh bones, left humeral head, left acromioclavicular articulation and multiple ribs. Tumor markers resulted negative except prostate specific antigen (PSA: 500 mgr/ml) and prostatic acid phosphatase (PAP: 208 U/l); prostate biopsy showed an undifferentiated carcinoma. The patient was submitted to right percutaneous nephrostomy, chemotherapy (PEB, cisplatinum, etoposide and bleomycin for 6 cycles) and ormonotherapy (LHRH analogues) reporting a clinical partial response. After 6 months the disease progressed and was started a second line chemotherapy. After 18 months from diagnosis patient is still alive with progressing disease. Our patient represents, with respect to many features, an original clinical case of prostate carcinoma occurring in young age, for the atypical association of an undifferentiated carcinoma with high levels of PSA and PAP and with osteoblastic-pattern of bone metastases. Further studies would be useful to identify new risk factors for development of prostate cancer in young men in order to achieve early diagnosis.