The motility rate of sperm during capacitation process was determined by calculating a sperm motile efficiency index (SMEI) using a hemocytometer. The SMEI values for the sperm from 100% of normal fertile men and 64% of infertile patients increased significantly by the fourth hour of incubation, while for 36% of infertile patients there was no increase. A correlation between the increase of SMEI and original motility, original SMEI and original semen amount was not possible. In addition, a decrease of the SMEI value was observed after sperm incubated for 3 hours were added to the seminal plasma of the donor. It is concluded that in human spermatozoa "hyperactivation and dehyperactivation" can be measured by SMEI.