Genotoxicity of indoor air pollution from biomass burning was evaluated in buccal epithelial cells (BECs) of 85 pre-menopausal Indian women who were engaged in cooking with biomass (wood, dung, crop residues) and 76 age-matched control women who were cooking with cleaner fuel liquefied petroleum gas (LPG). DNA damage was evaluated by comet assay and fast halo assay (FHA). The concentrations of particulate matter with aerodynamic diameters of less than 10 and 2.5 μm (PM(10) and PM(2.5), respectively) in indoor air were measured by real-time aerosol monitor. Generation of reactive oxygen species (ROS) was measured by flow cytometry and the level of superoxide dismutase (SOD) by spectrophotometry. Compared with control, BEC of biomass users illustrated 2.6-times higher comet tail % DNA (32.2 vs. 12.4, p < 0.001), 2.7-times greater comet tail length (37.8 μm vs. 14.2 μm, p < 0.001) and 2.2-times more olive tail moment (7.1 vs. 3.2, p < 0.001), suggesting marked increase in DNA damage. FHA also showed 5-times more mean nuclear diffusion factor (9.2 vs. 1.8, p < 0.0001) in BEC of biomass users, confirming sharp rise in DNA single strand breaks. Airway cells of biomass-using women showed 51% rise in ROS generation but 28% reduction in SOD, suggesting oxidative stress in the airways. Indoor air of biomass-using households had 3-times more PM(10) and PM(2.5) than LPG-using families, and DNA damage showed positive association with PM(10) and PM(2.5) levels controlling education, kitchen location and family income as potential confounders. In summary, chronic inhalation of biomass smoke elicits oxidative stress and extensive DNA damage in BEC.