CONTACT EQUIVALENCE OF MONGE-AMP\`ERE EQUATIONS WITH TRANSITIVE SYMMETRIES Dimitry V. Tunitsky Key words: Monge-Amp\`ere equation, characteristic bundle, contact equivalence, characteristic affine connection, invariance with respect to parallelism, contact symmetry, homogeneous M-A equation. 1991 Math. Subject Classification: 58G03, 58G16, 53C07, 53C30. Abstract: This paper deals with Monge-Amp\`ere equations on 5-dimensional contact manifolds, i.e., M-A equations with two independent variables. If a M-A equation is in general position, then the unique affine connection can be put into correspondence with this equation in natural manner. This correspondence allows to formulate and prove a number of results on contact equivalence of M-A equations with transitive symmetry group using suitable properties of affine connections.