DNA ploidy and cell cycle analysis by flow cytometry is used to obtain additional information about the diagnosis and prognosis of different types of cancer. However, there are several disagreements among authors about the tissue source (fresh-frozen or paraffin embedded), cellular dissociation methods (mechanical, enzymatic or other), use of different dyes, lasers, analysis software with different mathematical models and interpretation of results. A discussion about the different aspects that affect the study of DNA ploidy and cell cycle and a consensus in publications is mandatory. A strict control of analysis processes and data interpretation is also necessary.