We have submitted bilayers of La(OH) 3 Cu and multilayers of La(OH) 3 SrOCu to energetic heavy ion irradiation at 300 K and 700 K in order to investigate the possibility of preparing La 2CuO 4 and (La 1 − xSr x) 2 CuO 4 through the ion beam mixing technique. For comparison purposes, similar samples were annealed at 700 K. Results are given concerning the modification of the atomic compositions (La, Sr, Cu, O and H), the atomic depth distributions, the compound formation, induced either by irradiation or by thermal annealing. The specific role of the ion beam mixing process is emphasized.