The catecholamines in the recurrent and superior laryngeal nerves of the rat were assayed by high performance liquid chromatography. The nerves were shown to contain high levels of dopamine (1.9 +/- 0.6 and 2.3 +/- 0.4 pmol, respectively) and noradrenaline (1.3 +/- 0.3 and 0.9 +/- 0.2 pmol, respectively). No adrenaline could be detected in any of the nerves. Reserpine markedly depleted the stores of these amines in both nerves. A significant increase in dopamine level was seen in the superior laryngeal nerve after treatment with a monoaminoxidase inhibitor, but not in the recurrent laryngeal nerve. The high levels of dopamine detected are presumably derived from endoneurial paraganglia which were demonstrated by glyoxylic acid-induced fluorescence. The source of noradrenaline is less evident, but noradrenaline is probably stored in both endoneurial paraganglia and in sympathetic nerve endings.