Abstract
The MTT reduction assay is one of the methods used to evaluate the viability of sperm. In the assay, a tetrazolium component (MTT) is converted into MTT formazan by some specific enzymes in the viable cells. The amount of formazan product which is in theory directly correlated with the percentage of viable sperm is quantified by measuring the absorbance using a spectrophotometer. The present article compiles the MTT assays that have been used to determine sperm viability in most animal species and human. In each assay, other factors apart from the number of viable cells which potentially influence the accuracy and precision of results are stated, for instance, preparations of sperm and MTT solutions, length and conditions of incubation, a solubilizing agent as well as the formazan detection method. Also, strengths and shortcomings of the MTT test compared with others are summarized at the end of this article. This information may be useful for prospective researchers who are deciding to implement this colorimetric method in their experiments.

Key words: Colorimetric assay, Metabolic activity, Spectrophotometer, Sperm