Introduction: Seminal plasma proteins bind the sperm surface at ejaculation and may modulate several aspects of sperm activity during reproduction. DQH sperm surface protein, present in boar seminal plasma, shows affinity to phoshorylcholine, acidic polysaccharides, oviductal epithelium and zona pellucida glycoproteins. Materials and Methods: Monoclonal antibodies (MAbs) against DQH protein were prepared and used for determination of the DQH protein origin in boar reproductive organs, its localization on boar spermatozoa, and for investigation of its binding abilities in the porcine oviduct and to the zona pellucida of the oocyte. Results: The mRNA transcript of DQH protein was found in seminal vesicles, not in the testis, epididymis and prostate. Its translated products were immunodetected by MAbs in Abstract of the 8th Royan International Twin Congress, Tehran, Iran, 5-7 September 2007 Yakhteh Medical Journal, Vol 9, Sup 1, Summer 2007 17 seminal vesicle extract and fluid, on seminal vesicle tissue sections and on the membraneassociated acrosome part of ejaculated spermatozoa. Conclusion: These results confirmed the ability of DQH protein to bind the sperm surface at ejaculation and to participate in the formation of the sperm reservoir in the porcine oviduct. Moreover, monoclonal antibodies reduced binding of sperm to oocytes and proved the role of DQH protein in the spermzona pellucida primary binding.