This study was designed to determine if the value obtained after multiplying motile sperm concentration by seminal fructose concentration, named "true corrected fructose", correlates with sperm motility in asthenozoospermic men. Forty-two male partners in infertile couples were studied. Men were treated with 100 mg daily of clomiphene citrate for 5 days. Blood and semen samples were collected before treatment and 24 h after the end of treatment. Serum testosterone, seminal fructose and sperm motility were measured in each subject. Corrected fructose (log. sperm concentration multiplied by seminal fructose), and true corrected fructose (log. motile sperm concentration multiplied by seminal fructose) values were calculated. Prevalence of asthenozoospermia was 42.85% (18 of 42). Prevalence of hypofunction of the seminal vesicles was 9.5% using seminal fructose as a marker; 40.5% using seminal corrected fructose as a marker and 47.6% using true corrected fructose as a marker of seminal vesicle function. Regression analysis showed a better coefficient of determination between true corrected fructose and motile sperm concentration (R2=0.20, p < 0.001) than with corrected fructose (R(2)=0.05, p < 0.1) or fructose concentration (R(2)=0.006, p < 0.5). Asthenozoospermia was observed in 22.7% of subjects with normal function of the seminal vesicles, and in 65% of men with low values of true corrected fructose (z=6.02, p < 0.0001). Multivariate analysis showed that sperm motility grade 3 improved after treatment with clomiphene if true corrected fructose increased (p < 0.002). In those men whose seminal vesicle function improved after clomiphene treatment, a reduction in the prevalence of asthenozoospermia from 50 to 28.6% (z=3.10, p < 0.002) was observed whereas in those whose seminal vesicles did not respond to clomiphene the prevalence of asthenozoospermia was not reduced (z=1.05; p: NS). In conclusion, true corrected fructose measurement relates with sperm motility in cases of asthenozoospermia. Asthenozoospermia improves with clomiphene treatment if seminal vesicle function improves after treatment.