The method of biological dosimetry based on registration of frequency of chromosome aberrations in peripheral lymphocytes was proven to be a valuable technique for estimation of large absorbed doses. In the case of low absorbed doses or low dose rate the suitability of this method is restricted because of deficiency of suitable dose-response curve for yield of chromosome aberrations. In this work chromosome aberration rate was estimated in 31 ameliorators of the Chernobyl accident with the known data of physical dosimetry in the range of 12-30 cGy. Linear dependence of induction of chromosome aberrations was found in this dose range. The coefficients for induction of dicentrics and all unstable aberrations of chromosome type was found to be 1.4 +/- 0.4 and 7.2 +/- 1.2 per 100 cells per 1 Gy, respectively.