Airways obstruction in microwave-popcorn workers has been attributed to inhalation of flavoring agents. Two former workers at a microwave-popcorn plant were found by lung biopsy to have bronchiolitis obliterans. The study's aim was to determine whether exhaled nitric oxide (FENO) levels were associated with exposure levels, respiratory symptoms, or airways obstruction. A questionnaire, spirometry, and FENO measurements were completed by 135 workers. The FENO levels of workers with high flavoring exposures (n = 107) were compared with those of workers with low exposures (n = 28) and healthy external controls (n = 31). FENO levels were significantly lower in the high-exposure group (p < 0.05). There is no indication that FENO is useful as a marker of lung injury in a flavoring-exposed worker population with a substantial lung disease burden, but the finding of low FENO in the high-exposure group should not be dismissed.