An effective method for the isolation and purification of exfoliatin which has been recently reported by Melish and others as the staphylococcal toxin responsible for the scalded skin syndrome and the physicochemical properties of the purified toxin were described. From an active crude toxin produced by one of the clinical isolates of phage group 2, four types of toxic proteins which were all capable of causing the typical Nikolsky sign in neonatal mice were obtained and designated A, B, C, and D toxins. They had a molecular weight of about 24,000 and showed the same serological features in neutralization and precipitation tests, but were different from each other in showing a different single band with their respective mobilities in polyacrylamide disk electrophoresis. They were precipitated between pH 4.0 and 4.5 and lost their exfoliative capabilities. The resulting precipitates, however, could be solubilized in acetate buffer containing 0.5% sodium dodecyl sulfate, restoring their toxicities to almost the same extent as before. They were all stable when heated at 60 C for 60 min and at 100 C for 20 min, but lost their toxicities when heated at 100 C for 40 min. Additionally, the present authors observed that some staphylococcal strains not belonging to the typical phage group 2, isolated from patients with the scalded skin syndrome, were also capable of producing a similar but serologically unrelated exfoliative toxin.