© 2017, Scibulcom Ltd. All rights reserved.In this study our aim is to investigate the possible effects of Ehrlich ascites tumor (EAT), vitamins C and E on testis immunohistochemically and ultrastructurally. Swiss albino male mice were divided into a control, EAT, EAT + vitamin C, EAT + vitamin E, EAT + vitamin C + vitamin E groups. All treatments were applied for 10 days. After the experiment, testis tissues were taken and PCNA, APAF-1, AT-1 primary antibodies were stained immunohistochemically and also all the tissues were evaluated by electron microscopy. PCNA immunreactivity was seen on spermatocytes-1 and spermatogoniums, APAF-1 immunreactivity was seen on spermatocytes-1 and AT-1 immunreactivity was seen on Leydig cells in all groups. Control and EAT + vitamin E groups had a similar immunreactivity for all antibodies. In ultrastructural evaluations, interconnectional opening was seen on adluminal compartment and also no mature spermatids were seen in testis in all groups except the control group. EAT caused some structural and functional defects on testis probably due to the oxidative stress which was induced by the tumor in the body and also the treatment of vitamin E protected testis better than vitamin C.