By flow cytophotometry it is possible to obtain a DNA frequency distribution of cell nuclei. The curve is the result of the superposition from the 3 compartments: G0 + G1, S and G2 + M. Basing on a model, published formerly we simulated curves with different parameters. For our model we made the following assumptions: The G1- and the G2-peak are log-normal Gaussian distributions with the same coefficient of variation. The superposition of the 3 compartments is made after logarithmic classification and standardisation to the normal distribution. A program was developed for iterative approximation of the simulated curve to the measured values from the flow histogram. 7 points are needed for approximation and the standard deviation in changed step by step. In this way the moiety of the 3 compartments can be obtained. By cytophotometry it is only possible to estimate the relation between the number of cells in the 3 phases. The relative length of a cycle phase influences the shape of the DNA histogram, e.g. a relative prolongation of the G2-phase produces an increase of the G2-(4c)peak. The relationship between cell cycle and DNA histogram is influenced additionally by the cell kinetic in a different way in steady state or in exponential growth. By new measuring and staining methods it is possible to differentiate between several compartments, e.g. between G0 and G1. The flow cytophotometry is a valuable method to gain information about the cell kinetic.