In this paper we will introduce a new light distribution technique we term `Constructive Occlusion'. Using the geometry of Constructive Occlusion, diffuse surfaces can be used to tailor the distribution of a light source, eliminating the need for refractors or reflectors. The use of diffuse materials alone does not enable the tailoring of the distribution because lambertian materials distributed light as a cosine distribution. This cosine distribution is largely independent of the specific shape of the surface. Constructive Occlusion overcomes this limitation by the use of its patented geometry. Through application of the geometry, an integrating cavity is formed using a highly reflective diffuse material (>95% reflectivity). A mask is placed over the cavity, such that the light source and major portion of the cavity is occluded, enabling an interaction between the cavity and the mask. The arrangement and dimensions of the cavity opening, the mask, and the distance of the mask from the cavity, as well as several other geometric relationships, combine to control the light distribution of the optic. Contrary to expectations, we have been able to demonstrate our ability to shape the light distribution while maintaining high optical efficiencies, as high as 87% dependent upon the distribution. The specific techniques of constructive occlusion and example applications will be discussed in this paper.