Transrectal sonography of prostate was sensitivie to textural changes produced by both benign prostatehyperplasia(BPH) and prostate cancers. During recent 4 years, twenty cases of BPH and twenty cases of prostatecancers proven histologically were analyzed in their sonographic featurs, retrospectively. by using transrectalprostate sonography and suprapubic prostate sonography. The resutls were as follows: 1. Mean weights of BPH and prostate cancers was 40.4g and 47.6g, respectively. 2. Sonographic features of BPH revealed isoechogenecity in 11cases, homogeneity in 18 cases, well defined capsular margins in 19 cases, and calcification in 16 cases. 3. Sonographic features of prostate cancers revealed mixed echogenecity in 14 cases, inhomogeneity in 15 cases,poorly defined capsular margin in 14 cases, and calcifications in 13 cases. 4. Authors concluded that prostatesonography were valuable diagnostic modality in the differentiation of BPH and prostate cancers.