In 1959 and 1961 Herzberg and Shoosmith reported the vacuum ultraviolet spectrum of the triplet state of CH2. The present study focuses on a characterization of the upper state, the 3d Rydberg ((3)A(2)) state, observed at 1415 Angstrom. The theoretical interpretation of these experiments is greatly complicated by the presence of a lower-lying (3)A(2) valence state with a very small equilibrium bond angle. Ab initio electronic structure methods involving self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), complete active space (GAS) SCF, state-averaged (SA) CASSCF, coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], CASSCF second-order (SO) CI, and SACASSCF-SOCI have been employed with six distinct basis sets. With the largest basis set, triple zeta plus triple polarization with two sets of higher angular momentum functions and three sets of diffuse functions TZ3P(2f,2d) + 3diff, the CISD level of theory predicts the equilibrium geometry of the 3d Rydberg ((3)A(2)) state to be r(e)= 1.093 Angstrom and theta(e) =141.3 deg. With the same basis set the energy (T-e value) of the 3d Rydberg state relative to the ground ((X) over tilde(3)B(1)) state has been determined to be 201.6 kcal mol(-1) (70500 cm(-1)) at the CCSD (T) level, 200.9(2) kcal mol(-1) (70270 cm(-1)) at the CASSCF-SOCI level, and 200.8(9) kcal mol(-1) (70260 cm(-1)) at the SACASSCF-SOCI level of theory. These predictions are in excellent agreement with the experimental T-0 value of 201.95 kcal mol(-1) (70634 cm(-1)) reported by Herzberg.