To investigate the relationship of seminal plasma levocarnitine with sperm concentration, vitality and motility.Enrolled in this study were 64 infertile men, who were divided according to the results of routine sperm tests into a normozoospermia (n = 12), an oligozoospermia (n = 16), an asthenozoospermia (n = 20) and an oligoasthenozoospermia group (n = 16). The level of seminal plasma levocarnitine was detected by LC-MS-MS, the concentration of seminal plasma testosterone measured by chemiluminescence immunoassay, the correlation of seminal plasma levocarnitine with sperm concentration, motility and vitality determined by bivariate correlation analysis with SPSS15.0, and so was the correlation between the carnitine and sperm concentration by partial correlation analysis with seminal plasma testosterone as a control variable to exclude the influence of testosterone.The concentrations of total seminal plasma levocarnitine, free seminal plasma levocarnitine and seminal plasma acetolevocarnitine were (91.33 +/- 40.49) mg/L, (40.89 +/- 24.13) mg/L and (50.44 +/- 21.90) mg/L; the Pearson coefficients of correlation of the levocarnitine level with sperm motility, vitality and concentration were 0.161 (P = 0.235), 0.114 (P = 0.370) and 0.637 (P < 0.001), those of free seminal carnitine with sperm motility and vitality were 0.325 (P = 0.024) and 0.316 (P = 0.029), respectively, with the oligozoospermia group excluded, and that of partial correlation between the concentrations of seminal levocarnitine and sperm was 0.641 (P < 0.001).The level of seminal plasma levocarnitine is positively correlated with sperm motility and vitality, and more significantly with sperm concentration.