The antigenic properties of α-type and β-type toxins purified from Tityus serrulatus (Ts) venom were analysed by radioimmunoassay, using rabbit antibodies raised against Ts VII, the main β-type toxin in the venom, and against Ts IV, an α-type toxin. The anti-Ts VII serum did not recognize either the other β-toxins Ts I and Ts II or the α-toxin Ts IV; the anti-Ts IV serum did not bind any of the three β-toxins Ts I, Ts II or Ts VII. Thus, Tityus toxins display at least three distinct antigenic reactivity patterns. © 1993.