In this series of experiments the treatment consisted in the exposure to chrysotile fibers for 48 h followed by three period of recovery in normal culture medium: 24 h, 48 h and 72 h.The distribution of the nuclear DNA content of control cells showed a main peak in 2C region (DNA index = 1), and the values were distributed mainly between 2C and 4C, for mononucleated, bi or multinucleated cells.