OBJECTIVE: To investigate the injury on isolated testes induced by ischemia/reperfusion(I/R), and the protective effect of Yisheng injection on the injury. METHODS: Twenty-six isolated cadaver testes contributed by 13 persons were preserved with 4 degrees C 250 ml hypertonic citrate alloxuric (HCA) solution and then reperfused with 37 degrees C 500 ml HCA. Solution of experimental group contained 500 micrograms/ml Yisheng injection. In simple cold preservation test, involving in 8 experimental and 8 control testes, a series of time points (6, 12, 18, 24, 36, 48, 60, 72 hours) were set to harvest. 10 testes (1 testis respectively on 6, 12, 18, 24 and 36 hours in experimental and control groups) were reperfused with 37 degrees C HCA for 6 and 12 hours. Histological and histochemical changes were observed. RESULTS: In the experimental testes, 4 degrees C cold preservation in 24 hours could not induce obvious pathologic changes. After 24 hours, changes such as swelling, vacuolar degeneration or detachment of endothelial cells (ECs), separation between basement membrane and seminiferous epithelium, mal-alignment of spermatogenous cell and edema of mesenchyme could be observed. In the testes preserved for 12 hours, the activity of lactic dehydrogenase(LDH) and succinic dehydrogenase (SDH) increased, then fallen after 24 hours. The activity of Nitric oxide synthetase(NOS) decreased after 18 hours. All changes were more obvious after following 37 degrees C reperfusion. In the control testes, swelling and vacuolar degeneration of ECs occurred on 12 hours cold preservation, and injury was worse along with the prolongation of cold preservation time. Pathologic changes of ECs, seminiferous epithelium and mesenchyme were serious after 37 degrees C reperfusion. CONCLUSION: 4 degrees C cold preservation in 24 hours can only cause mild ECs’ injury, and obvious abnormal testes’ histological profile can be observed beyond 24 hours. 37 degrees C reperfusion will make injury worse. Yisheng injection can keep isolated testes histologic structure well in 24 hours cold preservation, and it has protective effect on I/R injury.