We have carried out three case-control studies on the relative risk of head and neck cancer in association with indoor air pollution. The studies performed at the Department of Otorhinolaryngology of the University of Heidelberg comprised 369 male patients with squamous cell carcinomas of the oral cavity, pharynx and larynx; one thousand, four hundred and seventy-six healthy subjects were used as controls and were matched for sex, age and residential area. The relative risk (RR) of laryngeal cancer related to daily exposure to fossil fuels due to stove heating with oil, coal, gas and wood in a period longer than 40 years was 2.5 [confidence interval (CI): 1.51-4.05]. After adjustment for tobacco and alcohol the RR declined slightly to 2.0 [CI: 1.10-3.46] but was still significant. Increased risks were also found for daily exposure in a kitchen containing air oil, coal or wood oven for a period longer than 40 years (RR = 1.7; CI: 1.01-2.71). In this latter group the RR because 1.4 after adjustments for use of tobacco and alcohol [CI: 0.76-2.41]). The RR of pharyngeal cancer related to daily exposure to fossil fuels due to stove heating with oil, coal, gas and wood in a period longer than 40 years was 3.6 [CI: 2.04-6.41]. After adjustments were made for tobacco and alcohol, the RR declined slightly to 3.3 [CI: 1.43-7.55] but was still significant. Elevated risks were also found for daily presence in a kitchen with oil, coal or wood ovens for a period longer than 40 years (RR = 1.6 [CI: 0.89-2.77].(ABSTRACT TRUNCATED AT 250 WORDS)