Significant improvements in the result of cancer treatment have resulted in longer survival for many of these patients and increasing numbers of patients who are cured. Unfortunately, the toxic effect of cancer therapy on other organs, and particularly the lung, has become an increasingly recognized problem in these patients. There are no specific tests that are diagnostic for chemotherapy or radiation-induced lung injury so the clinician must keep this diagnosis in mind and attempt to evaluate other possibilities. If treatment induced lung injury is considered likely, whether radiation pneumonitis or drug-induced pneumonitis, corticosteroid therapy may be of benefit. Therapy should be initiated at high doses and then tapered slowly following the clinical response. Most of these patients will do well, however, pulmonary toxicity may lead to respiratory impairment or mortality in some patients. Hopefully, as we gain more understanding of the risk factors and mechanisms of treatment-induced lung toxicity, new methods will be developed to decrease lung impairment due to cancer treatment.