Individual differences in tooth discoloration have been observed after using chlorhexidine mouth rinses. To study the correlation between retention of chlorhexidine and the discoloration tendency, two groups,‘stainers’and‘non-stainers’, were selected. The following parameters were tested: initial retention of chlorhexidine in vivo, retention of chlorhexidine to saliva-coated hydroxyapatite in vitro, and prolonged release of chlorhexidine in vivo. The initial oral retention of chlorhexidine was identical for the two groups, whereas in vitro retention of hydroxyapatite and prolonged release of chlorhexidine in vivo were higher among‘stainers’.