We investigated the G1 and S phases of synchronization using sodium n-butyrate, MTX and excess thymidine. The flow cytometry system was employed for cell cycle analysis while the receptor assay was adopted dextran coated charcoal (DCC) and the wash method. The results were as follows: S phase synchronization by MTX was 138% (control 100%) and by excess thymidine in the block and release method 210%. G1 phase synchronization by sodium n-butyrate was 140%. The progesterone receptor level, by E2 priming increased to 1.45 fmol/ug DNA being more than five times that of the control PR. The estrogen receptor level increased to 18.29 fmol/ug DNA in the G1 phase synchronization, seven times that of the control ER. From this study, the functional increase of the steroid receptor was most significant in the G1 phase.