In pulmonary sarcoidosis, alveolar macrophages undergo epithelioid transformation, and their increase and activation in bronchoalveolar lavage (BAL) samples serve as quantitative surrogates of disease activity. The study analyzed 16 biopsy-confirmed cases of sarcoidosis and 4 healthy controls, where they cytocentrifuged the cells, stained them with Diff-Quik®, and quantified the cell area of 50 randomly selected alveolar macrophages per subject (1000 in total). In patients with sarcoidosis, large/extra large macrophages constituted 41% versus 14% in controls (p < 0.001). Characteristic features of activation included vacuolization, rosette formation, and membrane undulation. These features were strongly correlated with serum ACE and sIL-2R, but not with the BALF CD4/CD8 ratio. They used nonparametric tests and principal component analysis (PCA) to evaluate associations. The enlargement and activation of alveolar macrophages are reproducible and can help in the assessment of sarcoid activity and response to treatment.