Sulfur sensitization of an octahedral silver bromide emulsion induces high-intensity reciprocity failure, decreases low-intensity reciprocity failure, and increases sensitivity for intermediate intensities. Addition of 4-hydroxy-6-methyl-1, 3, 3a, 7-tetraazaindene (TAI) sensitizes the sulfur-free grains at high intensities and desensitizes at low intensities. If the emulsions are developed without latensification, the addion of TAI to sulfur-sensitized grains sensitizes at high intensities and desensitizes at low intensities. If the emulsions are latensified before development, addition of TAI changes sensitivity very little at high intensities. TAI does not change the distributions of development centers among grains, provided the distributions are compared at equal values of mean number of centers per grain.