The glyoxylic acid-induced fluorescence method for localization of brain catecholamine neurons has been modified. Fluorescence is developed rapidly in cryostat sections of brains fixed by perfusion with 0.5% depolymerized paraformaldehyde and 2.0% glyoxylic acid. Since neither freeze drying nor vibratome sectioning is required, total processing time can be less than 1 hr. Both perikarya and fine varicose axons of norepinephrine- and dopamine-containing neurons can be seen throughout the neuroaxis. The modified technique retains good cytologic integrity and may provide a useful alternative for methods combining histochemical approaches.