The testicular spermatogenic stem and seminfferous tubular cells selectively synthesize heat shock proteins (Hsps) during heat stress. Hsps, synthesized from testicular cells and leukocytes, are identical in molecular masses as well as chemical properties. In this study, we induced the Hsps from leukocytes and investigated their in vitro effects on human sperm motility. Semen samples were divided into two parts, washed and unwashed. The whole blood was heated in 43℃for 15 minutes for induction of Hsps. A trans-membrane migration method was used to examine the effect of heated blood plasma on human sperm motility. The main heat-induced proteins of leukocytes were detected by 2-D electrophoresis and Comassie blue stain. Leukocytes treated by heat produced a large amount of Hsp72 and Hsp80, while only a small amount was observed in that of non-heated leukocytes. The heated blood plasma inhibited motility of washed sperm in a manner that was dose-dependent. In the presence of seminal plasma fluid, however, the inhibitory effects of heated plasma on human sperm motility could not be observed. It was concluded that the heat-induced substance(s) from leukocytes, which being highly possible the Hsps, interfered the mobility of wash human sperm and the inhibition might be antagonized by seminal plasma.