Summary. A simple method has been developed for washing spermatozoa: the cell suspension is layered over a solution containing Ficoll and, after centrifugation, the original suspending medium remains as an undiluted layer above the Ficoll solution while the spermatozoa form a loose pellet at the bottom. Removal of the supernatant layers is easily and completely accomplished by aspiration.
When ram spermatozoa were washed by this method, as much as 99·6% of the original medium could be removed during a single washing cycle, while up to 98% of the cells were recovered. Mechanical damage to the cells was minimal and repeatability was high.