Sarcoidosis is a multisystem disease with a 90% prevalence of lung involvement. It is now accepted that lymphocytes play a major modulatory role in the pathogenesis of this disease. However it has become evident in recent years that a number of other inflammatory cells capable of releasing mediators which can cause lung injury are involved as well. Although sarcoidosis is a relatively benign disease, it is well recognized that about 25% of the patients, perhaps those with unresolved injury, experience a relentless course and ultimately die from the disease. The rate of absorption from the lung of 99m Tc-DTPA is influenced by the integrity of the pulmonary epithelium, which might be altered as a result of injury to the lung. Several groups have measured 99m Tc-DTPA absorption in patients with sarcoidosis and have shown that it was increased in more than 50% of the patients studied. This abnormality seemed to prevail in patients with more advanced disease and in those who did not show a benign course. Whether a persistent increase in the rate of absorption of 99m Tc-DTPA reflects current or unresolved lung injury is unclear. The possibility of this technique being useful in monitoring the course of sarcoidosis deserves attention and should be further explored.