OBJECTIVE Patients diagnosed with non-specific interstitial pneumonia (NSIP) in 2 hospitals in Barcelona, Spain, were studied to investigate the factors that could contribute to the etiology of disease. METHODS The consensus diagnostic criteria established by the American Thoracic Society/European Respiratory Society were followed. The study included 16 patients, 10 men (65%) and 6 women (35%), all diagnosed with NSIP by open lung biopsy. Patients were questioned on pathological history, occupational or environmental exposure, medicinal drug use, contact with birds, and relationship with smoking. In addition, were recorded symptoms and physical signs, laboratory and respiratory function results, chest X-ray and computerized tomography scan features, fiberbronchoscopy findings and open lung biopsy findings. RESULTS Eleven patients (69%) -10 men (100%) and one woman (12%) -were smokers: 4 were active and 7 former smokers; 8 (80%) patients had fibrotic NSIP and three (50%) had cellular NSIP. Nine (56%) patients had a medication history, and 5 received chronic non-steroideal anti-inflammatory drug treatment. Occupational exposure to bleach, detergents, and ammonia or chloride products was documented in 6 cases. Three patients had contact with manufactured plastic products and isocyanate inhalation. CONCLUSIONS Smoking and medication use were prevalent in NSIP patients. Ibuprofen and celecoxib clearly provoked symptoms in one NSIP patient. Further studies are required to clarify the role of detergents, isocyanates and other occupation-related substances as triggering factors.