To detect the cholesterol ester transfer protein (CETP) levels in semen of infertile patients and evaluate the correlation between CETP in semial plasma and infertility.One hundred and sixty-three infertile patients and fifteen fertile males were selected randomly. The routine examination of ejaculates was fulfilled by computer aided semen analysis (CASA). The CETP levels in all seminal plasma samples and fifty-five serum samples were detected by ELISA method.The CETP levels in infertile patients and fertile males were (2.21 +/- 1.23) microgram/L and (1.40 +/- 0.45) microgram/L, respectively. There were no significant differences between the two groups(P > 0.05). And there were no significant differences of CETP levels in seminal plasma among groups of azoospermia(n = 29), oligoasthenozoospermia (n = 58), oligospermia(n = 15), asthenozoospermia(n = 44) and normozoospermia(n = 17) in the infertile patients(P > 0.05). The CETP in seminal plasma and serum were detected in 55 infertile patients, and there was no correlation between CETP levels in seminal plasma and serum using Spearman analysis(r = 0.009, P > 0.05). The mean CETP level in seminal plasma was almost 1/1,000 of that in serum.The CETP level in seminal plasma is extremely low and has no relation with the changes of sperm density or motility. It may ensure the integrity of sperm membrane before the sperm enters into female genital tract.