BACKGROUND Interventional cardiologists (ICs) are likely to receive high radiation exposure as a result of procedures they undertake. OBJECTIVE To assess the effects of low-dose X-ray radiation exposure on chromosomal damage and on selected indices of cellular and humoral immunity in ICs. METHODS The study population consisted of 37 ICs and 37 clinical physicians as the control group with similar age, sex and duration of employment, without any work-related exposure to ionizing radiation. Cytogenetic studies were performed by chromosome aberration analysis and immunological studies by flow cytometry, enzyme-linked immunosorbent assay and immunodiffusion techniques. RESULTS The frequencies of aberrant cells, chromosome breaks and dicentrics plus centric rings were significantly higher in the exposed group compared to the control group (P < 0.05; P < 0.01; P < 0.001, respectively), without positive correlation between the frequency of dicentric and centric ring aberrations and the cumulative doses of the ICs (r = 0.24, not significant). A significant increase was observed in the expression of activation marker CD69 on TCD4(+) stimulated cells in serum immunoglobulin G and interleukin (IL)-2 (P < 0.05) and a significant decrease in serum IL-10 (P < 0.05) in the ICs compared with that of the control group. There was no statistical difference between the two groups in terms of number of white blood cells and lymphocytes, CD3(+), CD4(+) and CD8(+) T cells, CD19(+) and CD16(+) 56(+) cells and concentrations of interferon (IFN)-gamma, IL-4, IL-6 and IL-8 cytokines. CONCLUSIONS While cytogenetic results show higher chromosomal damage, some immune responses are stimulated or modulated immunologically in ICs.