Oxides and their interfaces with polycrystalline InP are examined using complementary high‐resolution AES, SIMS, and XPS. The oxides, grown by low‐temperature dry and wet processes, are compared for composition and phase content. SIMS and AES depth‐composition data are used to compare the uniformity of the oxide layers and the composition of the interfacial region. Confirmation of impurity accumulation at the oxide–InP interfaces is presented, including buildup of elemental P and InP dopant, S. Other impurities assocaited with the growth of the wet oxide are found to be localized at the interface. Some evidence of impurity accumulation at grain boundaries at the wet‐oxide–polycrystalline‐InP interface is provided by SIMS and EBIC.