Electronic absorption and magnetic circular dichroism spectra for (CH3)(2)X, X = S, Se, and Te, in the vapor phase were measured in the range 2.5-5.3 mu m(-1) with a spectral bandwidth of less than or equal to 0.003 mu m(-1). The spectra show well-resolved vibrational structure for the n(X) --> (n + 1)p Rydberg system with positive MCD B terms for (CH3)(2)Se and (CH3)(2)Te, but a negative B term for (CH3)(2)S. The difference in the MCD spectra is interpreted in terms of the influence of magnetic coupling with the broad n(X) --> sigma* valence transition, which lies rather close in energy to the Rydberg system for X = S, but is separated to lower energy for X = Se or Te. The interpretation requires a n(X) --> sigma* transition assignment of (1)A(1) --> B-1(1) and provides support for the most recent (1)A(1) symmetry assignment of the n(X) --> (n + 1)p Rydberg excited state. The assignment of several weak, previously unreported, bands for X = Se and Te is also given.