Estrogens have been widely used for the treatment of advanced prostatic adenocarcinoma. However, their direct effect to prostatic cancer cells via estrogen receptors remains unclear. We investigated expression of ER alpha, wild-type ER beta (wtER beta), and a C-terminal truncated splice variant of ER beta (ER beta cx) in 50 benign and 100 malignant human prostatic tissue samples by immunohistochemistry. While strong immunostaining of ERa was consistently identified in the stromal compartment, wtER beta was expressed in epithelial cells in both the benign and malignant foci. However, wtER beta expression was significantly lower in the cancers than in the benign epithelium and inversely correlated with Gleason tumor grade (P < 0.0001 and P = 0.0099, respectively). In contrast, ER beta cx was significantly more expressed in the high-grade cancers (83%) compared with the low-grade tumors (22%) and the benign sites (11%) (P < 0.0001, both). Cancer-specific survival of patients with lower wtER beta expression was significantly worse than those with higher expression of wtER beta (P = 0.0018). Conversely, higher ER beta cx expression significantly correlated with poor cancer-specific survival (P = 0.0058). These results suggest that differential expressions of wtER beta and ER beta cx may be prognostic predictors for prostatic cancer.