A work-related interstitial lung disease has been diagnosed in workers at five nylon flock facilities in three different states and a Canadian province. The National Institute for Occupational Safety and Health hosted a workshop at which consulting pulmonary pathologists reviewed lung tissue samples from all the cases for which lung biopsy material was available (15 of 20 cases known in January 1998). After independent review and scoring of these lung tissue specimens, the pathologists reached consensus that the histopathological findings revealed a characteristic lesion-a lymphocytic bronchiolitis and peribronchiolitis with lymphoid hyperplasia represented by lymphoid aggregates. The pathologists noted that the pathological findings were distinctive when compared with known lung conditions. The clinical presentation for the cases generally included cough, dyspnea, restrictive ventilatory defect with reduction in diffusing capacity, and interstitial markings on chest radiographs or high-resolution computed tomography (HRCT) scans. Six of the cases improved after removal from workplace exposure without medical treatment. Six others, who had recovered with medical treatment and removal from the workplace, had relapses in both symptoms and objective findings after attempting to return to nylon flock work. With this and other evidence supporting the existence of chronic interstitial pneumonitis associated with nylon flock processing, workshop participants recommended surveillance for early identification of affected workers and their removal from further workplace exposure.