UNLABELLED The described method provides a new technique for differentiating areas of gray and white matter in fixed human brain slices. The technique is a modification of an existing method permitting use of the nonfading copper phthalocyanine dye alcian blue. Stained slices show turquoise gray matter that contrasts sharply with areas of white matter. PROCEDURE Cut human brains from gross anatomy laboratory cadavers into 4 mm slices and wash in running tap water for 12 hr. Oxidize slices in performic acid for 1.5 hr. Wash in running tap water for 12 hr. Stain slices in shallow dishes in 0.05% aqueous alcian blue. Wash in running tap water for 1 hr. Dry for 2-4 hr and embed in plastic.