Perfusion fixation with a mixture of paraformaldehyde and glyoxylic acid facilitates the histochemical demonstration of catecholamine-containing brain neurons. With this fixation, sections can be cut reproducibly with a cryostat and the fluorophore developed by immersion in glyoxylic acid without freeze-drying. Large sections of brain can be examined by fluorescence microscopy within 1 hour of fixation or stored for later examination. The properties of the fluorophore and the location of the fluorescent elements is identical with the neurons and terminal arborizations demonstrated by previous glyoxylic acid methods. Monoamine oxidase inhibition before fixation results in moderately increased fluorescence of terminals and perikarya, while all glyoxylic acid induced fluorescence is abolished by pre-treatment with reserpine. The rapidity and simplicity of this technique may make fluorescence histochemistry of central catecholamine pathways more accessible to psychopharmacologists.