To assess whether the phosphorylated Fas-associated death domain protein (FADD) at 194 serine (p-FADD) is valuable as a marker of biochemical recurrence in hormone-naive patients who had undergone radical prostatectomy.We used radical prostatectomy specimens from 106 patients. None of the patients had received neoadjuvant or adjuvant therapy. The percentage of positive p-FADD cells (nuclear staining) was immunohistochemically evaluated. The correlation between FADD phosphorylation and the clinicopathologic parameters was assessed. The correlation between the biochemical recurrence-free rate and the p-FADD expression level was analyzed using the Kaplan-Meier method.Overall, 39 patients developed biochemical recurrence. We investigated the expression of p-FADD in 106 patients with prostate cancer using immunohistochemistry. We compared our findings with the clinicopathologic parameters, including the follow-up data. Patients with a greater positive p-FADD rate had a significantly lower biochemical recurrence rate than those with a lower positive p-FADD rate (P < .001). A significant inverse correlation was found between the positive p-FADD rate and the Gleason score.A low expression of p-FADD could be a predictor of biochemical recurrence in hormone-naive patients who have undergone radical prostatectomy.