The Jahn-Teller effect in (X) over tilde E-2 CH3O is theoretically investigated in considerable detail. Making use of ab initio calculations carried out at the MRC-level we present the global shape of the adiabatic potential surfaces. Both sheets of the Jahn-Teller split (X) over tilde E-2 electronic state are used to determine the linear, quadratic and bilinear coupling constants of the e and a(1) modes, as well as selected third-order constants. Dynamical calculations for the vibronic structure have been performed with these parameters. The dynamical Jahn-Teller problem is solved by taking into account all the three e modes or, alternatively, two e modes and two a(1) modes. The resulting vibronic spectra are compared with those of previous work. Furthermore, ab initio calculated transition moments for (A) over tilde (2)A(1)<---->(X) over tilde E-2 are used to give an explanation for the forbidden Delta j = 3/2 transitions which were found by different experimental groups. (C) 2000 American Institute of Physics. [S0021-9606(00)30108-8].