Approximately 90% of the rural population use biomass for cooking and heating in developing countries and wood is one of the most commonly used.Exposure to wood smoke has been associated with respiratory diseases such as chronic bronchitis, asthma, and emphysema but there is little evidence about the participation of wood smoke in lung cancer pathogenesis.In a preliminary study, we examined 399 subjects with primary lung cancer and we found that 21.3% were nonsmokers with a history of continuous wood smoke exposure for more than10 years.The association between wood smoke exposure and lung cancer was found mainly in nonsmoker women probably because they are exposed to wood smoke for many hours per day (45%, 78 of 173 subjects).Adenocarcinoma was the most frequent lung cancer histologic type observed in our nonsmoker wood smoke exposed patients in both genders.