The distribution of light in a tissue is determined by it's optical properties. Several techniques are available for determining a tissues optical properties, and models are available for predicting the distribution of light within a tissue of known optical properties. The accuracies of these models were compared. The optical properties of neonatal skin were determined in the visible region from 450-750 nm. The reduced scattering coefficient, μ\sbs(1-g), increases directly with gestational maturity of the infant. The increase in the reduced scattering coefficient with gestational maturity is due to the accompanying increase in size and density of the collagen fibers. In neonatal skin, the optical density perceived by reflection, the depth probed by photons escaping from the surface, and their pathlength in the tissue are dependent on wavelength and on collection geometry. The penetration of visible light into neonatal skin is strongly dependent on wavelength and on gestational age.