This article aimed to estimate the mortality from exposure to passive smoking at work in Finland. The estimation used statistics on causes of death, exposure prevalences, and risk ratios from epidemiologic studies. The attributable fractions of cause-specific mortality from passive smoking at work were 2.8% for lung cancer, 1.1% for chronic obstructive pulmonary disease, 4.5% for asthma, 3.4% for ischemic heart disease, and 9.4% for cerebrovascular stroke. Altogether, about 250 fatalities were estimated to have occurred in 1996. This is approximately 0.9% of the total mortality in the Finnish population in the relevant disease and age categories. The magnitude of mortality related to past occupational exposure to passive smoking is considerable. Preventive measures to reduce environmental tobacco smoke in the workplace will be a powerful means of reducing the high burden of respiratory and cardiovascular diseases.