Interstitial pneumonitis has been described infrequently following administration of docetaxel, used alone or in combination with other chemotherapeutic agents or concurrent irradiation, for non-small-cell lung cancer (NSCLC). This toxicity is of special relevance in NSCLC, as clinical severity and differential diagnosis may be especially challenging. It seems to be due to type I and type IV hypersensitivity reactions to the drug. Clinical and radiographic features are nonspecific and diagnosis is made by exclusion. The rate of grade III–IV docetaxel-induced pneumonitis, ranging from 7 to 47%, depends on several factors, including total dose, chemotherapy schedule and especially concomitant docetaxel treatment with gemcitabine and radiotherapy. Although the usual outcome is cure, it sometimes eventually progresses to pulmonary fibrosis despite steroid treatment. This toxicity must be taken into account when planning treatment strategies for NSCLC in order to reduce its rate and to achieve prompt diagnosis and treatment.