This study was conducted to evaluate the percentage of viable sperm in ram semen by using the MTT reduction assay. Twenty ejaculates from 5 rams were included in this study. Semen samples were diluted with skim milk-glucose diluent to obtain a concentration of 30x106 sperms/ml. The rates of MTT reduction were taken in microtiter plates after one hour of incubation at 37oC using a Microplate Reader (DNM-9602) at a wave length of 550 nm. Simultaneously, split samples of the same semen were tested using the microscope and eosin-nigrosin stain. The correlation between the results of these tests was calculated using the Pearson correlation coefficients and Regression analysis. Results of the present study indicate that the values of sperm viability which calculated on the basis of MTT reduction rates were significantly (P<0.001) correlated with the results that simultaneously determined by the microscope and eosin-nigrosin stain, yielding regression coefficients of r2= 0.979. In conclusion, the MTT reduction test proved applicable as diagnostic tool for the quality evaluation of ovine semen. It can be used successfully in routine analysis, where practical aspects as time, costs and practicability are important.