Blood flow to the maxillary and mandibular gingivae was determined in 9 subjects under both normal conditions and in inflammation using the 133Xe clearance technique. A total of 36 sites (18 healthy and 18 inflamed) were selected for 133Xe injection. The clearance of radioactivity was monitored by a gamma camera. The calculated mean blood flows were 51.1 +/- 11.4 and 48.7 +/- 6.7 ml/100 g/min to the normal maxillary and mandibular gingivae, respectively. In inflamed gingiva, the corresponding mean blood flows were 55.0 +/- 13.0 and 54.7 +/- 11.7 ml/100 g/min, respectively. A statistical comparison of the healthy and diseased sites was done according to the paired t and Student's t tests. The difference between the sites was not significant (p > 0.05) in the maxilla, but significant (p < 0.05) in the mandible. There was no significant difference (p > 0.05) when the total healthy and diseased sites were compared.