Semen is a mixture of spermatozoa, produced by testicles, and seminal plasma secreted by accessory sexual glands and epididymis, to be combined at the time of ejaculation. Seminal plasma contains particles of different size wiich have effects on the spermatozoa viability and function during their transite along the female reproductive tract, and have the important physiological functions in different processes before penetration of a spermatozoon into an egg cell. These functions refer to as: nutrition, protection, regulation of motility and capacitation of spermatozoa, gamete recognition and binding. Knowledge of physiological characteristics of sperm and seminal plasma, influence of breed, lines and individual impacts of disorders, are prerequisite for further advancement in the reproduction efficiency and inheritance of the best traits of the semen genome. Knowledge regarding chemical composition of seminal plasma is very important in selection of the diluent, because it maintains and extends a lifetime of the spermatozoa during keeping of the semen. Biochemical parameters, such as lipids, proteins and minerals, participate in the metabolic and other process of spermatogenesis. Lipids are constituents of the cell membrane, participate in the metabolism and capacitation of spermatozoa, hiperactivation and acrosomal reaction as well as in the fertilization of an egg cell. Proteins participate in the capacitation and fertilization, in the transporationt of spermatozoa through female reproductive tract as well as they facilitate phagocytosis and binding of disfunctional spermatozoa. Minerals in the seminal plasma establish and maintain the osmotic equilibrium, they act as antibacterial agents, and are essential for the proper motility of spermatozoa., Some of them are components of the enzyms, while some participate in their activation. The studies regarding infertility, especially in man, are based more on analyzing and determing parameters of seminal plasma, because number and motillity of spermatozoa are not the only prerequisite for successuful fertilization. Namely, it is also necessary to have a quality medium for maintaining their normal characteristics. Seminal plasma plays an important role in the maintenace of the spermatozoa capable for fertilization. It provides the medium for their transport, enables protection from the oxidative stress and also provides essential nutrients for the capacitation and successuful fertilization.