Infliximab, a chimeric human/murine monoclonal antibody directed against the proinflammatory cytokine tumor necrosis factor alpha, is an effective therapy for Crohn's disease (CD) and rheumatoid arthritis refractory to standard medical treatment. We report a case of adult respiratory distress syndrome associated with infliximab therapy. A 33-year-old white male presented with an exacerbation of CD and was treated with his second infliximab infusion (15 months following the first infusion). Within 7 days he developed arthralgias, myalgias, and fever, followed by respiratory failure. He required intubation and mechanical ventilation. Open lung biopsy demonstrated eosinophilic pneumonia. Human antichimeric antibodies were present at high concentrations. An extensive investigation for infectious etiologies was negative. The patient was treated with intravenous corticosteroids, and fully recovered after a prolonged hospitalization. We review the infectious and immunologic complications of infliximab.