Based on the clinical impression of a relatively high number of non smoking women with COPD at a tertiary care facility in Saudi Arabia, we performed a case-control study to reveal possible risk factors. Our hypothesis was that the extensive use of incense burners among Saudis was a risk factor of COPD. Fifty consecutive patients with COPD and 71 healthy controls were questioned about risk factors of COPD. As expected more COPD-men than control men were smokers. Very few women smoked. We found no difference in the use of incense burners between cases and controls. On the other hand, two-thirds of the COPD-women and only 1/20 of the control women had been exposed to indoor open fire for more than 20 yr (P < 0.05). Accordingly, indoor exposure to open fire of wood or biomass seems to be a risk factor of COPD among Saudi women.