In 1994, union and management officials and local physicians in southeastern Michigan noted the occurrence among automobile production workers of respiratory illness consistent with hypersensitivity pneumonitis (HP). Local and national health authorities reviewed medical records, and in June 1994, individual employees and the union requested that CDC's National Institute for Occupational Safety and Health (NIOSH) evaluate potential occupational exposures associated with these illnesses. This report summarizes preliminary findings of the evaluation, including detailed information about one HP case and a summary description of the six biopsy-confirmed cases among automobile production workers from three different plants (plants A, B, and C) in southeastern Michigan; all six workers had jobs that entailed frequent exposure to metalworking fluids (MWFs). The findings suggest the need for further evaluation of a possible association of occupational exposure to MWFs with HP.