Gallo blue E, C. I. No. 51040, Mordant Violet 54, furnishes a blue black nuclear stain when applied to tissue sections in the form of its moderately stable iron lakes. This coloring combined well with such counterstains as orange G and eosin B. The Van Gieson stain tends to decolorize mucins, cartilage, and mast cells previously stained with this dye. Its aluminum lake solutions tend to gel in a few minutes to 24 hours depending on the solvent used and the amount of Al3+ present. Aluminum lake solutions give a moderately good blue to dark blue nuclear stain and a brilliant purplish red to dark purple stain to a variety of epithelial and connective tissue mucins. Acid dye counterstains are poorly tolerated. With either lake, nuclear staining is abolished by deoxyribonuclease digestion or relatively short mineral acid extraction of DNA.