In an evaluation of the possible chromosome damage caused by cytostatic agents 11 nurses with long-term exposure to such agents were studied. Five laboratory workers and 11 hospital clerks served as referents. The number of chromosomally aberrant lymphocytes was significantly higher in the group of nurses than in the group of laboratory workers or hospital clerks. The number of chromosome-type breaks was increased significantly among the nurses as compared to the reference groups. There was no significant difference in the number of chromatid-type breaks between the groups. The observed increase in chromosome-type aberrations may have been due to long-term occupational exposure to cytostatic agents.