Methotrexate is a commonly prescribed antineoplastic and immune modulating compound that has gained wide acceptance in the management of rheumatoid arthritis, psoriasis, sarcoidosis and a number of neoplastic disorders. Although generally considered safe and easy to use, methotrexate has been associated with a number of adverse reactions. Pulmonary toxicity has been well-described and may take a variety of forms. Pulmonary infiltrates are the most commonly encountered form of methotrexate pulmonary toxicity and these infiltrates resemble hypersensitivity lung disease. This discussion focuses primarily on low-dose methotrexate pulmonary toxicity and will discuss the diagnosis using clinical, pulmonary function, radiographical and pathological manifestations. Suggestions for clinical monitoring to detect adverse effects are given. In addition, management of pulmonary toxicity through discontinuation of the methotrexate, support and possibly the administration of corticosteroids is discussed.