Data are presented on modified spontaneous emission rates in quantum dot microcavity arrays. Three-dimensional optical confinement is achieved using apertured microcavities with square aperture sizes varied from 5 to 1 mu m on a side. A maximum measured increase in the on-resonance spontaneous emission rate over that off resonance is similar to 50%, and we identify this enhancement with apertured modes of the microcavity. Oscillations in the spontaneous emission rate versus wavelength correspond to spectral resonances in the higher order aperture modes. (C) 1999 American Institute of Physics. [S0021-8979(99)05206-8].