Several kinds of substances such as acids and bacterial toxins diffuse from dental plaque into the salivary film which moves slowly between the plaque on the teeth and oral mucosa. The volume of saliva retained in the mouth before and after swallowing seem to be very important with respect to clearance of such substances from plaque. In 30 subjects, five-year-old children of each gender, the volume of saliva in the mouth after swallowing (X) could be computed by measuring the potassium concentration in unstimulated saliva and in the expectorate after a five-second rinse with 3 ml of water immediately following a swallow. The volume of saliva normally swallowed was calculated from the unstimulated salivary flow rate and the normal swallowing frequency. The volume of saliva before swallowing (Y) was calculated as the total of (X) plus the volume normally swallowed. The unstimulated salivary flow-rate was 0.22 +/- 0.14 ml/min, the mean values of (X) and (Y) were 0.38 +/- 0.11 ml and 0.50 +/- 0.15 ml, respectively, and there were no significant differences in these values based on gender. These values were about half the values of those parameters in adults (Lagerlöf and Dawes, 1985), and insertion in the computer program (Dawes, 1983) of these values suggested that sugar clearance in the five-year-old children would be slightly faster than in adults.