Over the last few years, significant data have accumulated concerning components present in the seminal plasma such as hormones, enzymes, peptides, and cytokines [1-4]. This progress has led us to the discovery of other components in seminal plasma, not only in humans but in animals. We have achieved a greater understanding of the functional properties of these components, especially seminal plasma proteins in the male reproductive organs, its role in male fertility, and its immunological effects in vitro. Still, the physiochemical and functional properties of most of these proteins in seminal plasma remain unclear. Therefore, further investigation should be established to determine the complexities of these components present in seminal plasma and whether it has a role in the immunopathogenesis of diseases in the male and female reproductive systems. The protein makeup of seminal plasma appears to be extremely susceptible to variation on account of large number of factors, such as species, age, frequency of semen collection, the nature of ejaculates, the early ejaculates which show a protein profile different from that of the later ejaculates, the hormonal status of the individual, the condition of storage of semen, and possibly other factors such as diet, weather, environmental and emotional factors including stress. Unlike the other 332body fluids that are readily accessible for sampling and study, generation of semen, and therefore of seminal plasma, cannot be ordered about. The seminal plasma of all species is rich in proteins but some of the proteins are not indigenous to seminal plasma in that they may originate from serum. The proteins may also leak into the seminal plasma from dead spermatozoa or spermatozoa damaged during centrifugation or handling of the semen. Furthermore, some of the proteins of seminal fluid may be bound to the spermatozoa immediately after ejaculation and thus no longer be available in seminal plasma. The proteins in seminal plasma are contributed from secretions of various male reproductive glands, e.g., epididymis, seminal vesicles, prostate, and Cowper's and coagulating glands. The remaining proteins found in the seminal plasma have been divided into the following groups: proteolytic enzymes; glycolytic enzymes; nucleolytic enzymes; other enzymes; hormones and growth factors; antifertility factors; immunosuppressive factors; androgen-binding proteins; inhibin; immunoglobulins; and other nonenzymatic, nonhormonal proteins.