In spite of localization of gallium in the lungs in a large variety of inflammatory pulmonary diseases, the chest radiograph is and will continue to be the principal diagnostic tool for evaluation of pulmonary inflammatory disease. The 67Ga-citrate scan, however, serves as a study complementary to chest radiography because it indicates the extent, localization, and degree of activity of the inflammatory disease with greater accuracy than do the radiographic studies. It also permits the physician to follow progression of the disease or response to treatment and possible to detect disseminated interstitial disease not visualized on radiographs. Gallium-67 scanning may be used in the evaluation of patients with lymphorecticular neoplasms (Hodgkin's disease and malignant lymphomas) both during initial staging and in evaluation of the response to therapy. The 67Ga-citrate scan is useful in the evaluation of patients with lung cancer provided its limitations are kept in mind. It cannot and should not replace the pathologist's microscope. The scan is useful as a screening test only in patients who have radiographic lesions not consistent with inflammatory disease and in whom invasive diagnostic procedures or exploratory surgery are contraindicated unless the probability of detecting a resectable tumor is high. However, the limited resolution of the scanning system restricts the possibility of detecting lesions before they become radiographically visible. The histologic type of the lesion appears to have no effect on the probability of detection. As a noninvasive procedure, the 67Ga-citrate scan complements mediastinoscopy by indicating which lymph nodes should be biopsied. It is also useful in evaluation of the controlateral hilar node region. The scan frequently detects clinically unsuspected extrathoracic lesions. It may therefore be a useful initial procedure in guiding the work-up of the patient with a known or strongly suspected tumor. The combination of the 67Ga scan with the chest radiograph could provide the information necessary for presurgical clinical staging in patients who have no symptoms that suggest distant metastases. Gallium-67 scans may be useful in indicating the effectiveness of treatment and the sensitivity of a tumor to radiation.