To estimate the number of annual deaths, as well as the direct and indirect costs of occupational COPD and asthma, in the United States in 1996. Aggregation and analysis of national data sets collected by the National Center for Health Statistics, the Health Care Financing Administration, and other government bureaus and private firms. To assess mortality, we reviewed data from national surveys and applied a population attributable risk (PAR) of 15% for both asthma and COPD. We use a lower age limit of 35 years for occupational COPD and 20 years for occupational asthma. To calculate costs, we use the human capital method that decomposes costs into direct categories, such as medical expenses, as well as indirect categories, such as lost earnings and lost home production. We calculated proportionately adjusted costs for other plausible PARs. The 15% PARs result in costs of $5.0 billion for COPD and $1.6 billion for asthma. For COPD, 56% of costs were direct and 44% were indirect; for asthma, 74% were direct and 26% indirect. These estimates are conservative since we ignored costs associated with pain and suffering as well as the value of care rendered by family members. The proportionately adjusted costs for 10 to 20% PARs are $3.3 to $6.6 billion for COPD and $1.1 to $2.1 billion for asthma. The estimated $6.6 billion cost of occupational COPD and asthma in 1996 is likely to rise with the increasing prevalence of these diseases and warrants preventive intervention.