Abstract: Objective To observe testis injuries induced by in situ electroporation in specific pathogen-free (SPF) adult male Kunming mice. Methods With two sets of parameters of high and low voltages,respectively,in situ electroporation of the testis was performed in vivo by fixing the testis and epididymis of the mice between a pair of rectangular tweezer-type electrodes.Two weeks after electroporation,the mice were killed and the testis and epididymis separated and fixed with 4% paraformaldehyde after recording the weight of the testis.Routine histological sections were prepared and observed under optical microscope after HE staining.The epididymis was transfered into M16 medium for spermatozoa separation,and after dilution of the spermatozoa suspension,the spermatozoa viability was observed under optical microscope. Results Two weeks after high-voltage electroporation,examination of spermatozoa viability and microscopy of the testis sections revealed irreversible testis injury,and the testis weight was significantly reduced in comparison with that of control mice (P<0.01).Low-voltage electroporation,in contrast,only caused reversible injuries of the testis,and the male mice retained their repro-ductive capacity after a certain length of recovery period.The testis weight after low-voltage electroporation showed no significant difference from that of the control mice (P>0.05). Conclusions Appropriate setting of the parameters for in vivo electroporation may avoid severe impact on the reproductive capacity of the testis in SPF male Kunming mice.This technique also provides a possibility for exogenous gene transfer into the reproductive cells.