[The examinations for diffuse lung diseases]. 
Diffuse lung diseases show an abnormal shadow that is widely scattered on the bilateral lung fields in the chest X ray view and includes many respiratory diseases such as the infectious or the non-infectious disease; neoplasms. Among these, idiopathic pulmonary fibrosis(IPF) has been studied extensively because of its high frequency and difficulty of treatment. IPF is defined by the respiratory functions, the radiological findings, which depend on HRCT, and the histopathological evaluation by surgical lung biopsy. In particular, the histopathological appearance of usual interstitial pneumonia(UIP) is essential for the diagnosis of IPF. Most serum examinations such as angiotensin-converting  enzyme, anti-nuclear antibodies are applied to rule out other diffuse lung diseases. SP-D or KL-6, which is the marker of the type II epithelial cells, is thought to be very useful for revealing the disease activity, but since it is not increased in the early stages of IPF, it is not applied in the diagnosis of IPF.  The definitive serum examinations for the diagnosis or determinations of the therapeutic effect or prognosis of IPF have not been established. Easier, more useful and critical examinations including genetic diagnosis are required to manage patients with IPF.