division index and micronuclei frequency wereused to measure the biological effects of hepatoma SMMC-7721 cells irradiated withγ-rays. It is round that the living percentage is decreased significantly and themicronuclei frequency is increased with increasing dose. There is a negativecorrelation between the living percentage and the repair time for 0.68Gy
6.8Gy and136Gy irradiation
while there is a positive correlation between the micronucleifrequency and the repair time for 6.8Gy and 68Gy irradiation. The division indexesvary irregularly with the dose or the repair time after irradiation
probably due to thenon-synchronization of the cells.