Since the scintillation camera enables us to include lower thorax in the views obtained during Tc-99m colloid imaging of the liver and spleen, intrathoracic pathology may be identified as relatively cold or hot areas in the thoracic cavity. Eighteen patients who underwent Tc-99m sulfur colloid imaging during a one-year period were found to have intrathoracic pathology demonstrated either as photopenic areas or as areas of increased radioactivity. These patients' clinical data and the results of other diagnostic modalities, including autopsy, were correlated with the Tc-99m images. The intrathoracic disease processes recognized were bacteremia, two cases; pleural effusion, two cases; lung pathology, one case; and cardiomegaly, 13 cases. With the Exception of two patients with bacteremia who had substantial radiocolloid sequestration by the lung, all the other patients had hepatic dysfunction. The presence of compromised hepatic function allows the visualization of intrathoracic abnormalities: photopenia suggesting pleural fluid collection or an enlarged cardiac silhouette (either photopenia or increased radioactivity occupying a large space in the anterior view to yield cardiothoracic ratio of greater than 50%). Therefore, Tc-99m sulfur during colloid liver-spleen imaging, patients with hepatic dysfunction may incidentally demonstrate intrathoracic pathology, especially cardiomegaly.