The genetic changes in rats with radon exposure were studied by the micronucleus technology and detection of hypoxanthine phos- phoribosyl transferase (hprt) mutations.The rate of the micronuclei in peripheral blood lymphocytes and tracheal-bronchial epithelial cells in the radon-inhaled rats was higher than that of the controls (P<0.05).A similar result was obtained from the hprt assay,which showed a higher mutation frequency in radon-exposed rats.Our results suggested that micronuclei rate and hprt deficiency could be used as biomarkers for the genetic changes with radon exposure. The genetic changes in rats with radon exposure were studied by the micronucleus technology and detection of hypoxanthine phos- phoribosyl transferase (hprt) mutations. Rate of the micronuclei in peripheral blood lymphocytes and tracheal-bronchial epithelial cells in the radon-inhaled rats was higher than that of the controls (P <0.05). A similar result was obtained from the hprt assay, which showed a higher mutation frequency in radon-exposed rats. Our results suggested that micronuclei rate and hprt deficiency could be used as biomarkers for the genetic changes with radon exposure.