en Medical Genetics Medical Genetics Original Research Original Research The frequency of chromosomal aberrations was studied in the peripheral blood lymphocytes of 65 radiology technologists CRT) working at hospitals chronically exposed to x-rays. Although film dosimetry did not show the maximal annual permitted dose in any of the examined subjects, cytogenetic analysis detected fairly high levels of chromosomal aberrations in R T compared to unexposed controls. The mean frequencies of structural chromosome aberration per 100 lymphocyte metaphases of workers and the controls were 2.93 and 0.54 respectively, excluding the high level of achromatic lesions registered. The difference between them was statistically significant with a P-value of <0.05. Cytogenetic biomonitoring, Chromosomal aberrations, Lymphocytes, Low-dose x-irradiation, Occupational exposure. 43 46 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-461&slc_lang=en&sid=1 HOSSEIN MOZDARANI 20031947532846005454 20031947532846005454 Yes From the School of Medical Sciences, Tarbiat Modarres University, Tehran, P.O. Box 141554838, Islamic Republic of Iran. HAMID SAMAVAT 20031947532846005455 20031947532846005455 No