The surgical pathologist's role in the diagnosis of adverse pulmonary and pleural drug effect requires an appreciation of the clinico-radiologic scenario and particular knowledge of morphologic patterns of lung injury. Bronchoscopic biopsies may be helpful in some cases of DAD, eosinophilic pneumonia, or OP. Extrapolating patterns of lung involvement from small biopsies and cytologic preparations often is difficult and surgical lung biopsy is required. Although lung biopsies are not pathognomonic for drug toxicity and correlation with clinical, laboratory, and radiologic data is required, they can be a powerful tool in the evaluation of suspected drug-induced pulmonary disease by helping to exclude underlying disease or infection and documenting the pattern of lung injury. The latter information is helpful in making the diagnosis of drug toxicity as well as guiding the optimal management of the patient.