Attending animals of only one sex, depending on the chosen type of production, would considerably increase its effectivity. The problem of sex determination is an element of crucial importance in biotechniques of unconventional reproduction. In the case of cattle it gained importance with the development of breeding programmes based on multiple ovulation and embryo transfer (MOET). The control of proportions between sexes may be obtained either through separation (sorting) of spermatozoa subpopulations carrying chromosome X or Y, or by determining the sex of embryos (known as sexing) prior to their transfer to the uterus of the recipient cow. The current possibilities of sorting viable sperm are highly unsatisfactory for the needs of artifical insemination. Thus, for the sex preselection DNA techniques are being introduced, using the latest results on sex determining region Y (SRY) and on polymorphism of the gene of amelogenine. Introducing embryo-sexing into breeding programmes for cattle would result in considerable profits for the countries' economy. For instance, the annual genetic progress as regards milk production would reach 3 kg on the dam-son path and as much as 44 kg on the dam-daughter path.