Results from Phase 1 of this project indicated that transmission of S. mutans 6715 occurred among rats consuming 0, 0.1, 1, 5 and 56% sucrose in their diets. Generally, increased levels of infection were associated with increases in dietary sucrose concentrations. Recipient rats fed 0-5% sucrose showed mp difference in level of infection or any difference in smooth surface caries scores; those fed 56% sucrose attained the highest level of infection and also the highest caries scores of any group. Phase 2 of this project examined the transmission of S. mutans and subsequent caries development at intervals among rats consuming 0, 5 and 56% sucrose in their diets. Data from this phase are presently being assimilated for analysis.