In the management of infertile patients, it is well recognized that gamete intrafallopian transfer (GIFT) has a higher success rate than in vitro fertilization and embryo transfer. Oviducts produce unique proteins that may be responsible for the success of GIFT. Unique proteins from human oviductal fluid (hOF) have been purified in the authors' laboratory. One of these proteins of 54 kDa molecular weight, and containing carbohydrate, was obtained in a highly purified state. In this study, human sperm were incubated with: (1) a mixture of hOF-specific proteins, and (2) the highly purified hOF glycoprotein, designated human oviductin I (hOV-I). Using indirect immunofluorescence, the authors studied the ability of hOF proteins to bind to human sperm. The mixture of hOF proteins appeared to bind to the surface of the entire sperm. Conversely, hOV-I binding was restricted to the head region only. Studies are in progress to discern the function of the sperm-binding interaction(s) with hOF proteins.