Abstract: Objective: To investigate the expression and clinical significance of 4-hydroxynonenal (4-HNE) in prostate cancer. Methods: The 4-HNE expression of 67 specimens of prostate cancer tissue and 78 specimens of prostate hyperplasia tissue were detected by immunohistochemistry,and the relationship between its expression and the Gleason grade was analysed. The content of 4- HNE of prostate cancer and prostate hyperplasia patients and free prostate disease elderly men were detected and compared by ELISA. Results: The expression postive rates of 4-HNE in prostatic cancer and prostatic hyperplasia were 100. 00% and 2. 56% respecively, and their difference had statistical significance(P ＜ 0. 01) . There was no correlation between the expression of 4-HNE and Gleason grade(P ＞ 0. 05) . The contents of 4-HNE in the serums of prostate cancer patients were obviously higher than those of prostate hyperplasia and free prostate disease patients(P ＜ 0. 01) . Conclusions: The expression levels of 4-HNE are high in prostate cancer tissue and serum of patient. 4-HNE may play an important role on the mechanism of prostate cancer happens,which can be used to diagnose prostate cancer.