The authors conducted a matched case-control study of interstitial lung disease (ILD) using a self-administered questionnaire. All cases in the practice of two pulmonary specialists were identified. Cases were excluded if they were thought to have occupational exposures as a contributor, hypersensitivity pneumonitis or sarcoidosis, or some other well-recognized cause. Three controls were matched by sex and age (one year) as identified through orthopedic surgeons at the same institutions. Two rounds of a questionnaire were mailed; 17 cases (37.7%) and 94 controls (32.4%) responded to the questionnaire, although many of the case addresses were no longer valid. Individuals with ILD were 16.0 times as likely to report mold exposure and 11.1 times as likely to report silica as were controls in their workplace. Odds ratios associating ILD with moisture indicators in the home were in the same range as previously published associations between such indicators and wheezing. ILD may have environmental and occupational causes that warrant more systematic exploration.