Flocking is a widely used industrial process in which short segments of nylon or similar synthetic fibers are applied to backing fabric materials to produce plush material. Flock lung refers to a clinicopathologic syndrome that can be observed in workers in the flocking industry who are exposed to respirable microfibers. Clinically, the process closely resembles a hypersensitivity pneumonitis. Pathologically, the process also mimics hypersensitivity pneumonitis, but other lung injury patterns such as bronchiolitis obliterans organizing pneumonia and nonspecific interstitial pneumonitis may be present.