Oral mucosal effects of hydrogen peroxide mouth rinses were investigated in normal volunteers. Following a 2-week control period, 35 subjects were randomly assigned to rinse with either normal saline, 1/4-strength hydrogen peroxide (0.75%), or 1/2-strength hydrogen peroxide (1.5%), 4 times daily for 2 weeks. Mucosal status, buccal microbial adherence, salivary flow rate (SFR), and subjective reactions were assessed weekly. In the normal saline group, no significant changes were noted in any of the observed parameters and subjective reports were unremarkable. In both hydrogen peroxide groups, significant mucosal abnormalities were observed (p < 0.001) and subjective complaints were numerous. Bacterial adherence was significantly reduced in the 1/4 hydrogen peroxide group but not in the 1/2 hydrogen peroxide group. Despite reports of dry mouth, SFRs were not altered significantly. Since hydrogen peroxide rinses are associated with mucosal abnormalities and elicit overwhelmingly negative subjective reactions in normal individuals, they are not recommended for oral care.