Since histopathological examination was known to be the most sensitive evaluation for testicular toxicity, regulatory authorities have been published the guidelines on practical testicular assay approach. Those guidelines specified details of evaluation including fixation, embedding, stain-ing, histological examination and also seminiferous tubular staging methods. However, there have been confusing understanding among toxicologists and even pathologists on staging theory and its application on industrial testicular toxicity. Guidelines did not intend to conduct quantitative assay with staging but recommended the use of knowledge of staging. To count each tubular stage with statistical analysis is known to be time consuming and labor burdening work but the significance of toxicity has little value. It also has been pointed out that the application of staging theory for longer-term toxicity considered to be lacking of rationale. It could be recommended that qualitative assay with aware-ness of germ cell loss is more efficient method rather than quantitative counting of each tubular stage. Therefore it would be required that comprehensive understanding of testicular toxicity evaluation and the use of testicular staging method.