To　investigate　the　effects　of　experimental　left　varicocele　(ELV)　on　the　expression　of　sperm　associated　antigen　11　(SPAG11)　mRNA　and　its　protein　isomer　SPAG11E　in　the　testis　and　epididymis　of　adolescent　rats,　and　to　explore　the　mechanism　of　infertility　caused　by　varicocele.The　experimental　left　varicocele　model　was　established　in　the　adolescent　male　Sprague-Dawley　rats.　Two　and　4　weeks　after　the　operation,　the　changes　of　SPAG11　mRNA　and　SPAG11E　expression　in　the　testis　and　epididymis　were　detected　using　immunohistochemistry　and　reverse　transcription-polymerase　chain　reaction　(RT-PCR).The　expected　product　of　SPAG11　367　bp　amplified　by　RT-PCR　was　detected　only　in　the　epididymis.　SPAG11E　protein　was　observed　mainly　in　the　acrosomal　vesicles　and　acrosome　of　round　and　elongating　spermatids　of　the　seminiferous　epithelium,　in　the　cytoplasm　of　Leydig　cells,　and　in　the　supranuclear　region　of　principle　cells　and　stereocilia　of　the　epididymal　epithelium.　Imaging　and　statistical　analysis　showed　that　SPAG11　mRNA　and　SPAG11E　protein　expressions　in　the　left　epididymis　of　the　2-　and　4-week　ELV　groups　presented　a　remarkable　decrease　(P　＜　0.05　or　P　＜　0.01)　compared　with　the　right　side　and　the　corresponding　control　group,　and　the　same　decreased　change　in　the　left　epididymis　(P　＜　0.05　or　P　＜　0.01)　and　an　obvious　reduction　of　SPAG11E　immunopositive　reaction　in　the　right　epididymis　(P　＜　0.01)　were　noted　in　the　4-week　group　as　compared　with　the　2-week　group.　No　statistical　difference　of　SPAG11E　expression　in　the　bilateral　testes　was　found　(P　＞　0.05)　between　the　ELV　group　and　the　control,　as　well　as　between　the　2-　and　4-week　ELV　groups.SPAG11　is　a　specific　gene　expressed　in　the　epididymis.　The　localization　and　expression　of　SPAG11E　exhibited　a　region-　and　cell-specific　pattern　in　both　the　testis　and　epididymis　of　adolescent　rats.　The　expression　levels　of　both　SPAG11　mRNA　and　SPAG11E　protein　altered　obviously　in　ELV　rats.　The　results　suggest　that　SPAG11　may　not　only　play　an　important　role　in　spermatogenesis　and　sperm　maturation,　but　also　be　associated　with　varicocele-induced　male　infertility　or　subfertility.