A patient developed generalized anhidrosis, probably following sunstroke. Light microscopy showed an atrophic, deeply lobulated or elongated configuration of the eccrine sweat glands, most of them containing many vacuoles that possessed strong acid phosphatase activity. Electron microscopy revealed that the vacuoles were bound by a unit membrane and that the contents varied. Fusion of the vacuoles and accumulation of cellular debris in the lumen were also seen. It was concluded that the vacuoles showed areas of autolysis and were classified in the group of lysosomes. In addition, it is postulated that the anhidrosis resulted from a critical rise in body temperature with subsequent changes in the secretory cells.