Abstract: The cell cycle analysis and partialsynchronzation of a MNNG-transformed cellline(BHLB4)were carried out and the results obtained were as follows:cell generation time (GT) 11,6 hr, s 6.2 hr G2 1.3 hr, M1.8 hr G 2.3 hr, When this cellline was synchronized by 2x107 MMTX treatment for 14hr, the labelleu index reached:a peak of about 6o-70%1 hr, after release and the mitot;cintlex reached a peak of 3 -10%7 hr, after release, and could be further increased to about 20% in the prosence of 0.2ug/ml vincristme for 2, hours beefore harvesting.