Résumé : ARRHENIUS parameters of the alkaline hydrolysis of ethyl 3,4‐benzophenanthrene‐1‐carboxylate in water (15%) ‐ ethanol (85%) have been determined: E = 16,39 kcal, log PZ = 8,66, k2,(25°C) =4,40.10−4.These results indicate that the rate constant of this reaction is not affected by the non planar nature of the 3,4‐benzophenanthrene system. Copyright © 1959 Verlag GmbH & Co. KGaA, Weinheim