The Jahn-Teller distortion dependence of tetrahedral LaMnO3 and KCuF3 elastic tensor is derived using both direct uniform deformation differentiation of Jahn-Teller effect contribution into crystal energy and symmetry adapted energy Taylor series decomposition of W-Lat(EE) and W-Rel,l matrices. The tetrahedral LaNMO3 and KCuF3 are considered in D-4h(5), and D-4h(18) phases. It is shown that Jahn-Teller and direct relaxation terms are identical in both phases, whereas relaxation terms are not. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.