The distribution coefficients of Cd2+ and In3+ on crystalline antimonic(V) acid (C-AA) have been determined in order to find the best conditions for separation of both cations. Very high affinity of C-AA for Cd2+ ions enables to separate115mIn from115Cd in a single-step rapid procedure. The indium fraction obtained was very pure; the amount of radioactive contaminants was less than 0.0005%.