In this session we will look at how flow cytometry can be used to measure DNA content in mammalian cells. We will look at the available DNA dyes, the importance of sample preparation, cytometer set-up and how to perform the correct analysis. The session will be a mixture of theory and practical and we will be returning to the cytometer to give tips and tricks in machine set-up, pitfalls to watch out for and give a guide to best practices in this important application of flow cytometry. This session would be suitable for those beginning in flow cytometry and those who wish to learn more about cell proliferation but we will also be covering the general principles of cytometer set-up and current best practices in analysis.