Pulmonary toxicity and blood dyscrasias are rare side effects of sulfasalazine. Pulmonary pathology is variable, the most common being eosinophilic pneumonia with peripheral eosinophilia, and interstitial inflammation with or without fibrosis. We here present the case of a 68-year-old female patient treated for 6 months with sulfasalazine for rheumatoid arthritis. On laboratory examination, eosinophil count was 97 x 10(3) mm(3). Thorocoscopic biopsy was performed. Histopathologic diagnosis was bronchiolitis obliterans organizing pneumonia (BOOP). This is the first case in the literature to present with sulfasalazine-induced BOOP in a patient with seronegative RA.