We tested fluorescent and light microscopic markers to improve recognition of pituitary adenomas at biopsy. The optimal reagent was 100 mg/L of fluoresceinated Ricinus communis agglutinin 120 (RCA 120) lectin plus 3 mg/L of propidium iodide. The refrigerated solution was immediately available for use on routine frozen sections. The sections were stained for one minute and viewed immediately after they were rinsed with saline and coverslips applied. Fluorescein-labeled RCA 120, which binds galactose, localized vascular stroma. Propidium iodide, which binds nucleic acids, stained nuclei. Stromal configuration, nuclear morphology, and cell to stroma ratio were illuminated and used to distinguish adenoma from adenohypophysis. We also describe a method utilizing peroxidase-conjugated RCA 120 that demonstrates the same features by light microscopy. Fluoresceinated RCA 120-stained vessels and stroma of routinely processed material more reliably than hematoxylin-eosin or labeled antibody to fibronectin and faster than peroxidase-conjugated RCA 120 or the rapid method for reticulin.