SAPO-37 containing structural chromium(III) and iron(III) ions were tested as catalysts in liquid phase oxidation of benzene and cyclohexane, using hydrogen peroxide and tert-butylhydroperoxide as oxidants. Only chromium(III) is active as oxidation catalyst. In spite of the SAPO-37 framework stability under the reaction conditions, leaching of small quantities of chromium occurs and the observed catalytic reaction is mainly due to the chromium ions in solution. ??1999 Elsevier Science B.V. All rights reserved.