We have examined a new product, Uvitex 2B, for use as a nonspecific fluorescent stain for fungi and algae in tissue sections. Like Blankophor (BP) and Calcofluor (CF), this reagent binds chitin and cellulose in the cell walls of these organisms and fluoresces when exposed to ultraviolet light. BP and CF were both slightly insoluble at physiological pH (7.3), and solutions of these reagents became cloudy upon storage. Solubility was improved in weakly alkaline solutions (0.1 M NaOH), but staining efficiency was reduced at higher pH. These reagents did not stain all organisms adequately, and there was variable staining of some fungi. In contrast, Uvitex readily dissolved in phosphate-buffered saline (pH 7.3) and remained in solution for prolonged periods. All fungi and algae tested stained well with Uvitex, yielding an intense yellow-green fluorescence under fluorescein excitation conditions. Morphologic features of fungi demonstrated by the Gomori's methenamine-silver stain were clearly seen in Uvitex-stained sections. The speed, sensitivity, reliability, and ease of use suits Uvitex 2B for use in the frozen-section room, the clinical laboratory, or the physician's office.