Abstract-Monte Carlo calculations were performed to determine the backscattering from and transmission through concrete of 0.2, 0.5, 1.0, 2.0, 4.0, 6.0, and 10.0 Mev gamma rays. The radiation was assumed to be incident on a semi-infinite medium and on slab thicknesses of 0.5, 1.0, 2.0, and 4.0 mfp at angles of cos00 = 1.0, 0.75, 0.50, 0.25, and 0.10. The case histories of 5000 photons were followed on the IBM 704 digital computer for each of the 175 geometries (874,000 histories). The information obtained included: (1) The characteristics of emergent photons, which were stored on magnetic tape; (2) a routine that processes these characteristics to give polar and azimuthal angular dose distribution; and (3) detailed results from the application of the processing routine to the parameters investigated. The computer program, the processing routine, and the detailed results are given in ref. 1.