Spontaneous emission from dye molecules embedded in periodic dielectric structures was investigated. The structures consist of close-packed arrays of dye-doped polystyrene microspheres. Periodic arrays of polystyrene spheres with a submicrometer diameter were shown to provide a nonoverlapping gap or pseudogap in the visible spectral region. The modification of the spontaneous emission from inside the pseudogap structure was observed as a deep dip in the photoluminescence spectra. The alteration in the emission spectra is explained in terms of the partial suppression of radiation modes due to the periodic dielectric structures. ©1998 American Institute of Physics.