AbstractIntraoperative identification of Pneumocystic carinii generally involves the use of special stains, which are time consuming and require expertise. The hematoxylin-eosin (H&E) stain readily demonstrates the organism in smears but not in tissue sections. The method described affords identification of these organisms within 5-10 min. A smear obtained from bisected lung biopsy tissue is immediately fixed with cytosol spray, dried for a few sec, and stained with H&E. When slides are examined with either high dry or oil immersion objectives, the smear shows foamy amorphous clusters of organisms, macrophages, and epithelial cells. The method stains both the cysts and the trophozoites, and the results correlate with those from special stains on tissue sections. It is rapid, simple to perform, low in cost, and easy to interpret. (The J Histotechnol14:179, 1991)