The aim of this study was to evaluate the rates of salivary clearance at seven different locations in children. The diffusant was 1 mol/l KCl in a 1.0% agarose matrix, placed in small acrylic devices which could be fastened to the teeth with dental floss. The diffusion chambers were taken from the mouth at selected time intervals and the gels transferred quantitatively to flasks containing 400 ml of 100 ppm NaCl. The fluid was agitated intermittently for 1 h and analyzed for potassium by atomic absorption spectrophotometry. For 12 subjects (5 years of age), the clearance halftimes (the time for the initial potassium concentration to decrease by half) were lowest in the lower anterior lingual regions and were highest in the upper anterior buccal regions. When the salivary flow was stimulated, the clearance halftimes for the lower and upper anterior buccal sites in the 6 subjects without spaces between their anterior teeth were significantly higher than in the 6 subjects with spaces. The results show that the clearance halftime is longest for the upper anterior buccal site which is the site most prone to nursing bottle caries in the deciduous dentition.