The association between pulmonary obstruction (e.g., asthma) and occupational exposure to methyl cyanoacrylate (MCA) and ethyl cyanoacrylate (ECA) was examined in an occupational cohort of 450 persons at an adhesive production facility in Puerto Rico. Employee medical records containing information on physical examinations and pulmonary function tests (PFTs), as well as occupational histories, on each employee over a period of about 17 yr and industrial hygiene measurements were evaluated. The cohort analysis was based on a Cox proportional hazards model. Workers exposed to ECA or MCA were compared to workers unexposed to these chemicals with respect to their risk of becoming an ''incident case. An ''incident case was defined as any per son whose PFTs were normal at the time of employment, but later demonstrated an obstructive pattern, which was defined as a decline in the ratio of forced expiratory volume exhaled in 1 s to forced vital capacity (FEV /FVC) below 70%. A separate casecontrol analysis was also conducted that compared ''suspected cases, defined as all those whose PFTs ever demonstrated an obstructive pattern (e.g., asthma), to persons whose PFTs remained within normal limits throughout their employment with respect to their past peak and cumulative exposures to cyanoacrylates. All of these analyses showed no evidence that exposure to average short-term concentrations of ECA or MCA of less than 0.5 ppm and occasional daily peak exposures of at least 1.5 ppm (usually 10 min or less), with occasional higher concentrations during spills, were associated with an increased risk of pulmonary obstruction. However, the study suggested that persons occupationally exposed to cyanoacrylates were more likely to have some reversible eye or upper airway irritation than persons who were unexposed. 1