Objective To study the expression and its clinical significance of Oct4 in prostate cancer.Methods The Oct4 mRNA expression levels in 2 normal prostate (NP) samples and 8 prostate cancer (Pca) samples were determined by reverse transcription polymerase chain reaction (RT-PCR) analysis.The Oct4 protein expression levels in 10 NP samples,10 benign prostate hyperplasia (BPH) samples and 45 Pca samples were detected by immunohisochemical analysis.Results The relative expression levels of Oct4 mRNA were 0.91,0.76,0.66,0.63,0.55,0.50,0.48,0.42 in 8 Pca samples and 0 in 2 NP samples,respectively.The positive rates of Oct4 protein expression was higher in Pca tissues than in NP and BPH tissues (91.1％ vs.0.0％,91.1％ vs.0.0％,both P＜0.05).The level of Oct4 protein was increased with higher hostologic grade and clinical stage of prostate cancer.The strong positive rates of Oct4 expression were 72.7％ and 30.0％ in Pca tissues with and without lymph node metastasis respectively,and there was a significant difference in the strong positive rate between them (P＜0.05).Conclusions The Oct4 expression is closely related to the differentiation and invasion of tumor.Oct4 might be an important index for the prognosis of prostate cancer.