• In a series of 100 bilateral upper dorsal sympathectomies performed for palmar hyperhidrosis, gustatory sweating and other gustatory phenomena were reported by 68 of 93 patients (73%), followed up for an average of 11/2 years. These gustatory phenomena were quite different from physiologic gustatory sweating: a wide range of gustatory stimuli caused a variety of phenomena in varied locations. There was a negative correlation between the incidence of these phenomena and the occurrence of Horner's syndrome after sympathectomy. Analysis of our observations, and of clinical and experimental work of others, leads to the conclusion that gustatory phenomena after upper dorsal sympathectomy are the result of preganglionic sympathetic regeneration or collateral sprouting with aberrant synapses in the superior cervical ganglion.