Angiocardiography is an X-ray examination of the blood vessels or chambers of the heart for evaluation of the number and severity of blockages in arteries that supply blood to the heart. Cardiologists and staff members applying these procedures are exposed to high levels of scattered radiation. In the present study we analyzed and followed-up on the cytogenetic effects of X-ray angiography in personnel of laboratories for treatment of cardiovascular disease. According to film dosimeter analysis, personnel received 0.25-15 mSv during the previous year (average of 3 mSv/y), which indicated an exposure below the limit established by the International Commission on Radiological Protection (ICRP). Samples of peripheral blood were collected from cardiologists, nurses and technicians and from a matched control group. The incidence of unstable chromosomal aberrations (dicentrics, acentric fragments, ring chromosomes) and cytokinesis-blocked micronuclei were analyzed. Results show a high frequency of acentric fragments in cardiologists, nurses and technicians compared to controls (P < 0.001). When the exposed groups were compared, a higher percentage of acentric fragments was observed in the nurses and technicians compared to cardiologists (P = 0.004). Six individuals presented with dicentric chromosomes and their equivalent whole-body doses ranged from 0.05 to 0.10 Gy. No correlation was observed between chromosome aberrations and annual effective dose or age of the exposed groups. Although the mean frequency of chromosome aberrations in the male workers was slightly higher than in the females, no significant difference was observed between male and female workers in each group (P = 0.86). The mean number of micronuclei per 1000 binucleated cells was significantly higher in the exposed groups compared with the matched control group (P < 0.001). In a follow-up study, chromosome aberrations in lymphocytes of 23 exposed personnel were analyzed five times during 3 years. Results show that the mean number of acentric fragments decreased gradually during 36 months in those workers who followed the radiation protection guides. The results of this study emphasize the importance of individual biomonitoring, limiting exposure and radiation safety programs.