A staining procedure by modification of the "Mallory-azan" method, as adapted to the ant. pituitary of the rat, is descr. It is not claimed that the fundamental principle of the procedure is new; but because it invariably differentiates sharply the 3 classical cell types. Pituitaries are fixed in Zenker-formol soln., embedded in nitrocellulose and cut at 3-4[mu]. Sections are affixed to the slides, prior to the staining procedure, with the aid of albumin-glycerin, and nitrocellulose is removed with oil of cloves. After the sections are properly stained with azocarmine and treated with 5% phosphotungstic acid, as a separate step, they are stained with Mallory''s anilin-blue-orange-G mixture. It was found advantageous not to omit oxalic acid and to decrease considerably the amt. of phosphotungstic acid given in the formula. After the staining in this sol. is completed, sections are again treated with 5% phosphotungstic acid, followed by acidulated and distilled water (to eliminate the excess of anilin blue in the cytoplasm). Finally sections are dehydrated in absolute alc. and mounted in euparal.