The alkaline single cell gel electrophoresis (comet assay) was applied to study the genotoxic properties of silica in human peripheral blood lymphocytes (PBL). The study was designed to evaluate the DNA damage of lymphocytes and the end points like micronuclei from buccal smears in a group of 45 workers, occupationally exposed to silica, from small mines and stone quarries. The results were compared to 20 sex and age matched normal individuals. There was a statistically significant difference in the damage levels between the exposed group and the control groups. The types of damages (type I -type 1V) were used to measure the DNA damage. The numbers of micronuclei were higher in the silica-exposed population. The present study suggests that the silica exposure can induce lymphocyte DNA damage and produces significant variation of micronuclei in buccal smear.