The pathogenesis and underlying lesion of acquired idiopathic generalized anhidrosis (AIGA) are apparently heterogeneous. We report a patient with AIGA in whom the eccrine glands were histologically normal. However, electron microscopic examination showed markedly low numbers of nerve terminals and unmyelinated axons associated with the eccrine glands. Our laboratory investigations suggest that degeneration of postganglionic sympathetic cholinergic nerve may be the underlying pathogenetic mechanism of anhidrosis in this patient.