Semen analysis is carried out by conventional method by phase contrast microscope. But the assessment in terms of motility, velocity, swimming pattern, sperm head behaviour etc., may help in better understanding of the possible sperm function, semen quality and selection of suitable semen and bulls for cryopreservation. Various methods are used ranged from very simple techniques to the very sophisticated computer assisted techniques to estimate sperm motility and velocity parameters. Computer Assisted Sperm Analysis system yields accurate, objective assessment, repeatable, reliable results on different semen parameters and different velocity parameters based on the measurement of individual sperm cells. CASA is not only measure the proportion of motile spermatozoa but also measure other sperm motion parameters derived from individual sperm cells and it have more predictive power on fertility potential of semen ejaculates. It also provides a useful tool to study the effects of various in vitro procedures on sperm motility and hyper-activation. The book will be useful to the scientists, breeders and researchers working in semen production and preservation unit.