A general review of investigations of gamma-ray buildup factors is presented. Gamma-ray buildup factors for a point isotropic source in stratified spherical shields have been calculated using the one-dimensional gamma-ray transport code BIGGI-4T. The behavior of the buildup factor for stratified shields with respect to the behavior for the component materials differs between spherical and slab geometry. In addition to a material change effect, the buildup factor for a point isotropic source in stratified spherical shields suffers a density variation effect, which is much more prominent for configurations of heavier density followed by lighter density. The density variation effect can be eliminated by using a specially adjusted calculation of the stratified shields. It has also been found that energy absorption buildup factors in Goldstein and Wilkins’ data have relatively large uncertainties.