Polycrystalline oxide films were deposited by the spray pyrolysis technique on Al2O3 substrates. The atomic ratio in the initial spraying solution was Bi:Pb:Sr:Ca:Cu = 1.6:0.4:2:2:3. The chemical composition of the films was studied by EDX and ICP-AES analyses at different stages of the preparation process: after the pyrolysis, after annealing at different temperatures and after annealing at a constant temperature for different times. The results obtained reveal the reasons for concentration changes of the cations and make possible an optimisation of the composition of spraying solution in order to obtain single phase superconducting films. © 1997 Elsevier Science B.V.