Abstract —The efficiency of dietary instructions was tested in a group of 7–8‐yr‐old schoolchildren. The instructions were given in the presence of the child's mother either verbally (control groupn= 14) or both verbally and written (test groupn= 12). For this purpose the salivary status of the first grade pupils (n= 79) of a primary school in Turku was screened. Salivary flow, buffer capacity, sucrase activity, lactobacillus, yeast and S. mutans counts were determined. Children whose salivary lactobacillus count was over 104CFU/ml (n= 32) were selected for the present study. The efficiency of the dietary instructions was measured as a reduction of salivary lactobacilli. There were no differences in the number of children with reduced LB counts or in the caries increment of 1 yr between the test and the control groups. However, children who succeeded in reducing the number of salivary lactobacilli (42%) within 4 wk revealed a significantly (P<0.05) lower caries increment after 1 yr than the rest of the subjects. We concluded that children whose lactobacillus counts were reduced by the dietary instructions developed significantly less caries than children whose lactobacillus counts remained high after the instruction. No additional effect on lactobacillus counts and caries increment could be demonstrated by supplementing the verbal dietary counseling with written instr