This study aimed to observe the percentage of motility of human spermatozoa after passage through 20 per cent hen's egg yolk medium. Twenty-one samples of freshly ejaculated human semen having a sperm density over 20 million per ml and a percentage of motile sperm over 50 per cent were used in the study. The percentage of sperm motility was estimated under the microscope by conventional method. The sperm motility was evaluated within 30 minutes after ejaculation and every one hour thereafter for 8 hours. After the first observation, the semen was divided into two parts, one part kept as a control and the other used for the experiment. The latter was washed in Tyrode's solution and overlaid on 20 per cent egg yolk column and allowed to migrate toward the bottom of the column for two and a half hours. The spermatozoa at the bottom of the column were brought out and washed in Tyrode's solution. The percentage of the sperm motility was observed every hour for 5 hours. After passing through the 20 per cent egg yolk medium, percentage of sperm motility was observed to increase from 66.2 to 87.2 while that of the control declined to 49.3. Five hours after passing through the egg yolk medium the percentage of motile sperm was still high, an average of 80 as compared to 17.4 for the control. Results of this study indicate that hen's egg yolk has a sperm motility stimulating property. Whether hen's egg yolk can be used as a sperm motility stimulant in the treatment of such conditions as asthenospermia and oligospermia is subjected for further study.