High-resolution photoelectron spectroscopy is used to study the branching ratios for vibrational autoionization of Rydberg states of aniline (C6H5NH2) converging to the ground electronic state of the ion. By using two-color double-resonance excitation, it is possible to prepare autoionizing resonances in which two different vibrational modes are excited. Determination of the vibrational state distribution in the product ion provides information on the relative rates of autoionization for the two modes. It is found that some normal modes appear to be especially effective at promoting vibrational autoionization, while others appear to be completely ineffective.