During the conservation of feline semen, the freeze-thaw procedure in particular is responsible for inducing severe spermatozoal damage, which diminishes fertilizing ability. Therefore, cold-induced damage represents a limiting factor for the conservation of semen, particularly semen from felids, which are often affected by teratospermia. In this article, feline sperm characteristics are reported, with special reference to motility and morphology, which are more likely to be affected by conservation protocols; and moreover, the causes of cold-induced damages are described. Attention has been focused on methods to evaluate functional integrity of spermatozoa, and those applied to cat semen are reviewed. Among these, a rather recently developed technique involves fluorescent staining methods, and in particular chlortetracycline. The chlortetracycline assay applied to cryopreserved cat epididymal sperm shows that it is suitable to evaluate the functional status of cat sperm.