Nerve cells of the human striatum were investigated with the use of a newly developed technique that reveals the pattern of pigmentation of individual nerve cells by means of transparent Golgi impregnations of their cell bodies and processes. Five types of neurons are distinguished: Type I is a medium-sized spine-laden neuron with an axon giving off a great number of collateral branches. The vast majority of the cells in the striatum belong to this type. Numerous intensely stained lipofuscin granules are contained in one pole of the cell body and may also extend into adjacent portions of a dendrite. Type II is a medium-sized to large neuron with long intertwining dendrites decorated with spines of uncommon shape. A distinguishing feature of this cell type is the presence of somal spines. This cell type is devoid of pigment or contains only a few tiny lipofuscin granules. Type III is a large multipolar neuron. The cell body generates a few rather extended dendrites that are very sparsely spined. The finely granulated pigment is evenly dispersed within a large portion of the cytoplasm. Type IV is a large aspiny neuron with rounded cell body and richly branching tortuous dendrites. The axon branches frequently in the vicinity of the parent soma. Large pigment granules are concentrated within a circumscribed part of the cell body close to the cell membrane. Type V is a small to medium-sized aspiny neuron. The dendrites break up into a swirling mass of thin branches. More than one axon may be given off from the soma. The axons branch close to the soma into terminal twigs. Cells of this type contain numerous large and well-stained lipofuscin granules. Each of the cell types has a characteristic pattern of pigmentation. The different varieties of nerve cells in the striatum can therefore be distinguished not only in Golgi impregnations but also in pigment-Nissl preparations.