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				One of the most important aspects of frozen equine semen is the tremendous variation in "freezability" among individual stallions. Based on the clinical experience of SBS in both Europe and North America, data gathered on large numbers of stallions, using a variety of freezing techniques the following averages have been determined: 30% of stallion in the general population will be "good freezers" 40% will be "satisfactory" sperm from the remaining 30% will not survive the freezing process with a level of motility sufficient to be used for AI. Complicating matters, there is no direct relationship between fertility of frozen semen and fertility obtained with natural service or fresh semen AI. Because of this, the only way to determine whether sperm from a stallion will survive freezing and thawing is to collect and process a number of ejaculates and evaluate the post-thaw motility of representative straws from each ejaculate frozen. This gives us information on how well the stallion's sperm have survived freezing and thawing. Non-motile sperm have probably been damaged beyond repair and are incapable of fertilization. Motile sperm have retained their locomotive properties, which indicates better survival during processing. Unfortunately the retention of motility does not guarantee that sperm will be capable of fertilization. Damage to sperm membranes and the acrosome, which contain enzymes required for fertilization, can occur without adversely affecting motility. In this situation there are apparently normal sperm which are incapable of fertilization. Current research is aimed at developing laboratory tests to detect this type of damage in frozen-thawed semen samples. In today's competitive breeding industry, successful use of cooled transported semen is a must. Evaluation of the effects of dilution rate, extender type, and antibiotic toxicity on semen quality will optimize the success of a cooled semen program. Stallion owners need to know that they are using the best techniques to process their stallion's semen so that they can confidently ship the best possible product to their clients. A stallion's reputation can be severely and permanently damaged if mare owners are left with the impression that his semen "doesn't ship well". Although there are some stallions whose semen quality is not adequate to achieve good fertility with shipped semen, many stallions with good or even excellent quality semen will have their breeding reputations ruined simply because of improper semen processing techniques. We see a tremendous need for a voluntary independent testing program that can assess cooled semen quality to protect both mare and stallion owners. The following example assumes an average per cycle conception rate of 40%.    1st cycle  2nd cycle  3rd cycle  Total no. mares bred 20 12 7 20 total doses used 60 24 14 98 no. mares pregnant (40%) 8 5 3 16 final conception rate (3 cycles) = 80%