Electron-propagator calculations are performed on the vertical ionization energies of ethylene with a sequence of correlation-consistent basis sets. Two methods are employed: the nondiagonal, renormalized, second-order (NR2) approximation and the third-order, algebraic, diagrammatic construction. The computational efficiency of the NR2 method permits the use of the correlation-consistent, pentuple zeta basis, which contains 402 contracted Gaussian functions. As the size of the basis set grows, NR2 results for outer-valence ionization energies steadily increase; NR2 errors with the largest basis set are less than similar to0.15 eV. Agreement with prominent, inner-valence peaks is also satisfactory and the ratio of two pole strengths corresponding to inner-valence, (2)A(g) states is in close agreement with observed intensity ratios.