The alkaline single-cell gel electrophoresis assay or comet assay is a sensitive and rapid method for DNA strand breaks and detection of alkali labile sites at the single cell level, it further provides information on the presence of damage among individual cells. In this paper we explore the use of this technique utilizing exfoliated buccal mucosa cells from non-smokers (9 donors) and smokers (11 donors). The extent of DNA image length was found to be significantly increased in the smoker group (89.30 +/- 16.18 microns) than in the non-smoker group (52.01 +/- 10.43 microns). Our results indicate that the single-cell gel electrophoresis assay could be applied to human monitoring using exfoliated buccal epithelial cells.