Get familiar with mitotic cells. Evaluation of cells that are undergoing mitosis and non-dividing cells takes some familiarization. Use a cell biology textbook to become familiar with what mitotic and non-mitotic cells should look like. As a general rule, mitotic cells will appear as two cells in the process of splitting apart.
Examine your specimen. Using a microscope with the appropriate magnification requirements, properly focus your prestained tissue microscope slide. Your sample specimen should be appropriately stained so you can adequately identify cellular structures including the cell membranes and nuclei.
Count cells. Identify and count the cells that are either undergoing mitosis or are not dividing. Count each group individually using a hand-held counter and record your number for each.
Calculate the mitotic index. Using a calculator, sum up the total amount of cells you counted by adding the number of mitotic cells and non-dividing cells together. Divide the number of mitotic cells by the total number of cells you counted to calculate the mitotic index of your tissue sample. The mitotic index is the percentage of cells undergoing mitosis in your sample.