Tityus serrulatus scorpion venom was fractionated by gel filtration affording two heterogeneous toxic fractions, T1 and T2; the latter was further fractionated by ion-exchange chromatography. The fraction of T2 eluted with 0.15 M ammonium acetate buffer, originally named 'tityustoxin', was shown to be a pool of several proteins. One of them, TsTX, as well as T1, was also named 'tityustoxin'. The major and perhaps most potent toxin of the venom, gamma-toxin, was eluted with 0.30 M buffer as a highly purified protein and shown to be different from TsTX. gamma-Toxin is contained in both T1 and T2.