The adsorption and photodissociation of CH3Br(ad) on LiF(001) and NaCl(001) have been studied by temperature programed desorption (TPD) and angle-resolved time-of-flight mass spectrometry. The results of TPD on LiF(001) indicated that CH3Br(ad) formed a first adsorbed layer in which repulsive adsorbate-adsorbate interactions dominated. At high coverages, the TPD profiles on LiF(001) were characteristic of multilayer ("zero-order") desorption but at no time were separate monolayer and multilayer TPD peaks observed. In contrast, on NaCl(001) CH3Br(ad) formed a distinct monolayer phase before growth of the second and subsequent layers, Methyl radicals were produced by photodissociation of CH3Br(ad) at 193 nm on both surfaces at coverages from submonolayer to > 10 monolayers. The CH3(g) translational energy distribution, P(E-T’), exhibited two coverage-dependent photodissociation channels; the first, termed the "direct" (DIR) channel, observed at multilayer coverages, had a P(E-T’) centered at 2.4 eV, and the second, termed the "indirect" (IND) channel, had a P(E-T’) less than or equal to 1.8 eV. The mean energy and width of the DIR methyl, P(E-T’), was similar to that from CH3Br(g) photodissociation. This DIR channel peaked at approximately 25 degrees off-normal for LiF(001) and 38 degrees off-normal for NaCl(001), giving the most probable C-Br bond directions. The IND channel was comprised of CH3(g) which escaped from the adlayer after suffering an inelastic collision (including sometimes reaction) with neighboring CH3Br(ad) molecules. The DIR channel dominated at all CH3Br(ad) coverages on LiF(001) but the IND channel dominated at all coverages on NaCl(001), consistent with a model in which CH3Br(ad) on LiF(001) predominantly "stands up" and CH3Br(ad) on NaCl(001) predominantly "lies down." Polarized IR spectroscopy performed in this laboratory supports these geometries. There was a peak in the LIF(001) IND energy distribution centered at 0.9 eV and there were two peaks in the NaCl(001) IND energy distribution, IND(1) and IND(2), centered at 1.1 and 0.5 eV, respectively. These substantial but specific energy losses (compared with the energy of the directly photorecoiling CH3) are indicative of a strongly inelastic encounter with constrained dynamics, believed to be the exchange reaction CH3+BrCH3’(ad) --> CH3Br+CH3’ with retention of direction in the CH3’. The LiF(001) and NaCl(001) IND angular distributions, P(Theta’), were generally broad and of the form cos(n) Theta’ centered on the surface normal but there was evidence for retention of direction of methyls in the IND channel at multilayer coverages on LiF(001), characteristic of exchange reaction.