A simple new histochemical technique for the differentiation of adrenaline and noradrenaline storage cells is described. In both groups of cells two more types: clear cells and dark cells can be distinguished. The new technique is based on a special interaction taking place between the product of the reaction noradrenaline-glutaraldehyde and the metachromatic cationic dye. The relationship between clear- and dark cells observed by the described new technique and by electron microscopy by the other authors is also discussed.