Objective: To explore the possible mechanisms of growth regression of human androgen dependentprostate carcinoma cells caused by androgen withdrawal. Methods: After 24 h of treatment with 1×10-9mol/L dihydrotestosterone (DHT), the expression of phosphorylated ERK proteins and cell cycle regulationmolecules including CDK2, CDK4, CDK6 and P27kip1 in human androgen dependent prostate carcinoma cellline LNCaP was measured by West blot analysis 0 h, 8 h and 24 h of after androgen withdrawal. Humanandrogen independent prostate carcinoma cell line PC-3 was also examined as control. Results: Down-regula-tion of phosphorylated ERK, CDK2, CDK4 and CDK6 and up-regulation of P27kip1 were found initially inLNCaP cell line 8 h after androgen withdrawal. The levels of phosphorylated ERK and CDKs decreased con-tinuously and reached the lowest after 24 h, while continuous elevation of P27kip1 was detected thereafter to 24h. No expression change of phosphorylated ERK, CDKs and P27kip1 were detected in PC-3 cell line. Conclu-sion: The androgen withdrawal can cause ERKs activation decrease and cell cycle regulation moleculeschanges, which may be one of the mechanisms for inhibited growth of androgen dependent prostate carcinomaafter androgen ablation by either operative or medicine methods.