Worldwide, the annual morbimortality caused by cigarette smoking is a major public health concern. In Colombia, up to 33% of the adult population has smoked at some point in life, raising important national issues on the disease burden from tobacco. The aim of this study was to establish whether cigarette smoking increases the frequency of chromosome aberrations (CA) in peripheral blood lymphocytes of smokers (n = 52) compared with non-smokers (n = 52) in Popayán, Colombia. After signing a consent form, volunteers provided a blood sample (20 ml) to establish cell cultures at 52 h. For CA analysis, 100 complete metaphase cells from each subject were evaluated. The CA frequency was significantly higher in smokers (8.38 +/- 0.61) than in non-smokers (3.13 +/- 0.29), showing the highest number of CA (14.83 +/- 1.01) among heavy smokers (>20 pack-years). Interestingly, light smokers (< or =10 pack-years) also showed a significant increase in CA when compared to non-smokers (6.62 +/- 0.53 versus 3.13 +/- 0.29, P < 0.01, respectively). In addition, a significant positive correlation was found between the frequency of CA and the intensity of smoking in pack-years (R2 = 0.60). Our study indicates that the genotoxic effects in lymphocytes from smokers are most likely caused by cigarette smoke constituents, providing scientific evidence to encourage national campaigns to prevent tobacco consumption.