In this paper we present the cell cycle analysis using the latest flowcytometer, FACScan and dedicated softwares. Although the 5-bromodeoxyuridine (BrdU) and anti-BrdU method developed by Gratzner has become popular for analysis of cell kinetics, contaminating interstitial cells and cell doublets are still factors responsible for some mistakes in measuring the cell cycle accurately. These hampering cells were almost gated out on the catogram consisting of the forward scatter and DNA content (propidium iodide, PI). After that, the bivariate distribution of BrdU and PI according to the tumor growth showed reliable patterns. In LLC tumor the population, of which DNA content was compatible with S phase cells, was detected in the cytogram. Thus, the two-dimensional analysis of the cell cycle can demonstrate each population clearly. The results obtained from the BrdU method are more beneficial than autoradiography or microspectrophotometry, and reproducible data of the cell cycle parameters can be acquired with some devices described here.