IN THE etiology of dental caries, decalcification of enamel and dentin is accorded a prominent role.' The citrate ion under essentially neutral conditions will decalcify enamel and dentin in the rat when present in the drinking water.2' 3 When 1 per cent sodium citrate was added to a diet producing occlusal caries in the rat, no significant change in the caries picture was evident.4 Gustafson, Stelling, Abrahamson, and Brunius,5 however, found that the addition of 4 per cent sodium citrate to a purified diet producing caries in the hamster significantly reduced the cariogenicity of the diet.Although the presence of citrate in human saliva has been clearly established,6-10 no attempts have been made to relate its concentrations to various oral conditions* with the exception of some studies on dental erosion.7' 8 The primary purpose of the present investigation, therefore, was to study the relation between salivary citrate and dental caries experience. Since citrate is rapidly utilized by oral microorganisms,9 the streptococcus and lactobacillus populations were determined in order to establish if these 2 groups among the total oral flora could account for any change of citrate in saliva. EXPERIMENTAL Two groups of children, differing markedly in their caries experience, were selected as follows: the average number of DMF teeth of 12 to 14-year-old children who were permanent residents of Grand Rapids, Michigan, was 7.7 ± 4.4 and 8.9 ± 4.6 for the boys and girls, respectively, in 1949.12 DMFV scores varying from the mean by more than one standard deviation were placed in either the "low" or "high" DMF categories. Thus, a DMF score of 4 or less was considered low for both sexes, and a score of at least 12 for the boys and 14 for the girls was considered high. Only the data from 144 children available in both 1949 and 1952 are presented.Whole paraffin-stimulated saliva was collected in January, 1950, and in March, 1953, for citrate analysis by procedures previously described.8 '3 In March, 1953, only, the saliva sample obtained for citrate analysis was immediately followed by a second collection without preservative for the estimation of streptococci and lactobacilli. All samples were received within 48 hours after collection, streptococcus and lactobacillus counts made immediately, and the citrate analyses were carried out within 5 days.t