Conceived and designed the experiments: MAK VVP ML BK EAG TSG. Diagnosis and management of drug-associated interstitial lung disease Symptoms of drug-associated interstitial lung disease (ILD) are nonspecific and can be difficult to distinguish from a number of illnesses that commonly occur in patients with non-small-cell lung cancer (NSCLC) on therapy. Identification of drug involvement and differentiation from other illnesses is problematic, although radiological manifestations and clinical tests enable many of the alternative causes of symptoms in advanced NSCLC to be excluded. In lung cancer patients, high-resolution computed tomography (HRCT) is more sensitive than a chest radiograph in evaluating the severity and progression of parenchymal lung disease. Indeed, the use of HRCT imaging has led to the recognition of many distinct patterns of lung involvement and, along with clinical signs and symptoms, helps to predict both outcome and response to treatment. This manuscript outlines the radiology of drug-associated ILD and its differential diagnosis in NSCLC. An algorithm that uses clinical tests to exclude alternative diagnoses is also described. The diagnosis of drug-associated interstitial lung disease (ILD) involves three elements: clinical suspicion, differentiation from other parenchymal lung diseases using computed tomography (CT) and other clinical tests for alternative disease, and a compatible histological pattern. This review article will discuss the radiological evaluation of a patient with non-small-cell lung cancer (NSCLC) suspected of suffering from drug-associated ILD, the diagnosis and management of drug-associated ILD, and the development of a diagnostic algorithm designed to distinguish gefitinib ('Iressa')-associated ILD from other forms of parenchymal disease.