The epididymis and vas deferens store an important number of fertile spermatozoa called theextragonadal sperm reserves. These stored spermatozoa can be collected in an ultimate attemptto preserve viable spermatozoa of a critically ill or dying stallion. Epididymides are collectedvia routine castration. After cooled transport of the testicles and epididymides, spermatozoa arecollected either by retrograde flushing or by the float-up method. Retrograde flushing usuallyresults in a much higher sperm yield and is considered the method of choice. Epididymal spermatozoacan be frozen using standard freezing protocols.