A total of 604 metaphases were evaluated. Analysis included average 20 metaphases of at least 43 chromo­somes for each sample. We found structural aberrations in 3.47% of the metaphases. Aberration types of these chro­mosomes were determined as 46.15% of chromatid breaks, 24% of chromatid gap, 15.18% of isochromatid break, 7.69% of isochromatid gap and 3.84% of isochromosome. The effects of βC and PC were investigated separately and in combination, and compared against the chromosome damage produced in cell cultures with no Mit-C treatment (i.e., the effect of background radiation exposure) and with Mit-C treatment. A significant rise in chromosomal aberra­tions was observed with the addition of Mit-C (Table 1). We found that 7.8% of metaphases showed chromosomal abnormality with Mit-C compared to 1.9% in cultures without Mit-C (p = 0.03). The Mit-C-induced aberrations occurred in 4.8% of the cell cultures with added βC and in 4.1% in cultures with added PC. In cultures containing βC (10^–5M) + PC (0.015 μ g/mL) only 1.3% of the cells show­ed chromosomal aberrations compared with 7.8% of those containing Mit-C alone (p <0.05).