One hundred fifteen smokers working in a nuclear fuel manufacturing facility were analysed for various types of chromosomal aberrations. They experienced exposure for a period of 1-25 years. Their age ranges from 23 to 52 years. A total of 94 smokers and 118 non-smokers who were not exposed to uranyl compounds or to any other known mutagens and belong to the same age group formed the control subjects. The results showed that there is a significant increase in the frequency of chromosomal aberrations in the exposed smokers when compared to the control smokers. In the control group, the smokers showed a high frequency of chromosomal aberrations when compared to non-smokers suggesting clastogenic effect of smoking. Chromosomal aberrations observed in the exposed smokers could be due to the cumulative effect of both smoking and exposure to uranyl compounds.