Many studies have established a definite relatonship (both positive and negative) between the presence of certain trace elements (other than f) and prevalence of the disease of dental caries. Present studies with the cariogenic organism streptococcus mutans should give a better understanding of caries development and may suggest additional means of caries control. The objectives of the research are: 1. To define the requirements for and effects of certain trace elements on various growth parameters of S. mutans. 2. To determine the mechanism of uptake and transport of the trace elements by S. mutans through kinetic studies to measure the affinities, specificities, and energy dependence of the transport systems. The experiments are conducted in continuous cultures in a Teflon chemostat (designed and built by the Applicants for this research) that contributed minimal trace metal contamination during cultivation. A chemically defined medium (treated to lowr trace metal contamination and supplemented with high purity trace metals) is used. Controlled conditions of substrate concentration, trace element additions, oxygen tension, and pH are employed. Elements under study are Ca, Mn, Mg, fe, Cu, Co, Zn, Sn, V, Mo, Se, Cd, Ba, Sr, Li, Ni, and Pb. ?999