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 carcinoma of the oral cavity, pharynx, and larynx and 1476 healthy control subjects matched for sex, age, and residential area. The OR of laryngeal cancer related to daily exposure to fossil fuels due to stove-heating with oil, coal, gas, and wood for longer than 40 years was 2.5 (CI = 1.51 to 4.05). After adjustment for tobacco and alcohol, the OR declined slightly to 2.0 (CI = 1.10 to 3.46) but still was significant. Elevated ORs were also found for daily presence in a kitchen with an oil, coal, or wood oven for longer than 40 years (OR = 1.7, CI = 1.01 to 2.71; after tobacco and alcohol adjustment, OR = 1.4, CI = 0.76 to 2.41). The OR of pharyngeal cancer related to daily exposure to fossil fuels due to stove-heating with oil, coal, gas, and wood for longer than 40 years was 3.6 (CI = 2.04 to 6.41). After adjustment for tobacco and alcohol the OR declined slightly to 3.3 (CI = 1.43 to 7.55) but still was significant. Elevated ORs were also found for daily presence in a kitchen with an oil, coal, or wood oven for longer than 40 years (OR = 1.6, CI = 0.89 to 2.77; after tobacco and alcohol adjustment, OR = 2.5, CI = 1.03 to 6.30).(ABSTRACT TRUNCATED AT 250 WORDS)