The visible photoluminescence from thin films of silicon nanocrystallites produced by a pulsed laser ablation supersonic expansion source has been studied to determine the role of particle surface and size in the emission behavior. Variation of nanocrystallite size and surface through a variety of chemical treatments and processing steps has shown that the visible emission can be explained using only a simple quantum confinement model. Particle size has been reduced through a series of acid etch and reoxidation cycles and compared to sample emission wavelength. The role of surface species in determining emission behavior has been studied by chemically altering the surfaces and comparing their surface properties as determined by x-ray photoelectron spectroscopy to their photoluminescence behavior. Nanocrystallite size controls the emission energy, while surface passivation only determines emission intensity, through control of excited carrier recombination pathways.