To investigate the effects of transplanted endothelial progenitor cells (EPCs) on the spermatogenic functions in testicular detorsion. Bone-marrow-derived EPCs were obtained from rats and transfected by enhanced green fluorescent protein adenovirus (Ad-eGFP). The rats were divided into 3 groups (n = 6 each). In the sham group, left testis was not twisted. In the ischemia reperfusion injury (IRI) group, 1 ml saline was injected into the femoral vein of each rat after testicular detorsion. In the EPCs group, 1 ml EPCs suspension (1.0 × 10(6) EPCs) was injected into each rat after testicular detorsion. The Ad-eGFP transfected EPCs were injected into the 3 additional rats of testicular torsion-detorsion. At Day 5 post-transplantation, the characteristics of transplanted EPCs homing were detected. And the pathological changes and apoptotic cells/seminiferous tubules in left testis were examined. When the value of multiplication of infection (MOI) was at 50, the transfection rate of EPCs by Ad-eGFP exceeded 73.7%. At Day 5 post-treatment, the cells exhibiting green fluorescence were detected in left testis. The germ cells in rats of the sham group were normal. And the ratio of apoptotic cells to seminiferous tubules was 0.09 ± 0.02. The germ cells in rats of the IRI group were much fewer. And the ratio of apoptotic cells to seminiferous tubules was 2.82 ± 0.81. As compared with the IRI group, seminiferous epithelium was thicker in the EPCs group. And the ratio of apoptotic cells to seminiferous tubules was 0.32 ± 0.09 in the EPCs group. It was much smaller than that in the IRI group. There was significant difference (P < 0.01). The transplantation of EPCs is effective for treating the spermatogenic dysfunctions caused by testicular torsion so as to greatly enhance the spermatogenic functions.