Improvement of staining and measuring methods for DNA or cell cycle analyses by flow cytometry (FCM) has been continued by many researchers for years. Japan Cytometry Society (JCS) and the organizations which were past of JCS have borne the central role in Japan. Now, the application range of FCM is greatly expanded and to operate FCM machine became very easy. This paper has been written for the purpose of recognizing again the notes for improving coefficient variation(CV). It is necessary to understand that CV value and DNA histogram may be influenced on various factors. Furthermore, it is important to understand about a possibility of changing the DNA amount of G0/G1 cells or the affinity between double strands DNA and propidium iodide can change, when we analyze DNA histogram.
