Gallium-67 citrate ((67)Ga) is known to accumulate in inflammatory areas. Though the exact mechanism of the transportation and localization of (67)Ga citrate in foci of inflammaion is still obscure, (67)Ga scintgraphy has been used clinically to evaluate patients with interstitial pneumonia with regard to disease activity and progression. Quantitative analysis using (67)Ga scintigraphy has been attempted several times, but the results have been inadequate, even with computer analysis. In this study, the combination of (67)Ga scintigraphy and bronchoalveolar lavage (BAL) was applied to patients with various types of interstitial pneumonia to estimate quantatively (67)Ga accumlation in the lungs. The radio activity of BAL fluid and peripheral blood were measured directly, and the ratio of radioactivity of BAL fluid/peripheral blood was calculated for each of the patients. Radioactivity in the peripheral blood was contained mainly in the plasma. On the other hand, most radioactivity in BAL fluid was shown to be located in the cellular component. The cellular component of BAL fluid was separated by culture in plastic culture plates into adherent cells (macrophage-enriched fraction) and non-adherent cells (lymphocyte-enriched fraction). Comparison of radioactivity of each cell fraction proved that alveolar macrophages contained most of the (67)Ga citrate in BAL fluid. Therefore, the high (67)Ga uptake in scintigrams of patients with interstitial pneumonia represents the increased number or activated state of alveolar macrophages in the lungs. The direct measurement of (67)Ga radioactivity in BAL fluid could be a useful method to analyze quantatively (67)Ga scintigrams of interstitial pneumonia patients.