Abstract: The iodide distribution in the silver iodobromide grains of a high-speed ammonia-cal emulsion is investigated in relation to the instant of time of iodide uncorporation into the emulsion during double-jet precipitation.The X-ray photoelectron spectro-scopic study confirms the general concept that the earlier the iodide incorporation, the less the possibility for the ions to come out to grain surface, and vice versa.However.as shown by X-ray diffraction analysis, with the shift of the instant of iodide incorporation from the end of the precipitation toward the beginning of the process, there occurs an increasingly narrowing of the diffraction profile of the grains, which implies an increasingly more uniform distribution of the iodide, ions through the grains.This "homogenization effect" in the grains, associated with an early iodide incorporation, is believed to be a consequence of a relatively long recrys’tallization and, hence, redistribution process of the silver iodide or silver iodobromide grains formed at the early stages of precipitation.The iodide-containing grains formed by the end of the precipitation are offered less chance of recrystallization and, therefore, a more uneven distribution of the iodide ions in the grains results.In all cases, the surface layer of the grains shows an iodide content considerably higher than might be expected based on a uniform distribution.One of the reasons for the surface enrichment with iodide ions could be the tendency of the grains for a reduction of the lattice distorsion which would arise to a greater extent with more iodide ions incorporated in the grain bulk.