PIP: A study was undertaken to examine the influence of pH on the migration of X and Y sperm as observed in freshly ejaculated semen samples from human donors. These sperm were allowed to migrate into capillary tubes containing media of varying pH. Y-carrying sperm were i dentified using flourescent staining with quinacrine dihydrochloride. S mall changes in pH were ineffective in influencing the ratio of sperm. 6 additional samples were analyzed in a more acid pH resulting in an insignificant change in migration. This study indicated that the percentage of Y-bearing sperm migrating through a capillary tube is unaffected by the medium's pH. Evidence suggest the unlikelihood that X and Y sperm can be differentiated on the basis of migration through media of varying pH.