An intervention designed to test the influence of cognitive restructuring on protective oral health behaviors was conducted with 108 patients with mild to moderate gingivitis. Subjects in the experimental group viewed slides of active, mobile bacteria taken from their mouths on 5 occasions: before and after prophylaxis and at 3 appointments, one month apart. A specially trained hygienist discussed with these participants the process of periodontal disease, the role of bacteria, and self-efficacy (self-control) for oral hygiene self-care. Both experimental and control group subjects received instruction in oral self-care procedures. Assessments of oral health using Löe and Silness' plaque and gingival indices (PI and GI) were taken throughout the study and at 3- and 6-month follow-up visits. Self-efficacy, oral hygiene intentions, attitudes, and values comprised the set of cognition variables. Plaque and gingival indices mean differences between groups approached significance at visit 6. Analyses were also performed using percent of gingival surfaces scored at "0" (no visible bleeding on probing). A trend occurred for group differences in percent "0" scores at visit 6, with the experimental group maintaining higher percent zeros (better health) at this 3-month follow-up. At visit 7 (9-month follow-up), PI and GI differences disappeared. No significant differences were found between groups for oral health cognitions or behavior reports over time. The data suggest that the cognitive-behavioral intervention produced a delayed relapse in protective oral self-care behaviors, and by extension, oral health status. Such a delay could be clinically relevant in promoting adherence to oral hygiene behavior between professional visits.