PURPOSE: To evaluate the clinical efficacy of two commercially available, fluoride-free, alcohol-free mouthwashes containing either 0.075% or 0.07% cetylpyridinium chloride (CPC) in controlling established dental plaque and gingivitis compared to a non-antibacterial control mouthwash. METHODS: A 6-week double-blind, randomized clinical trial was conducted in Trujillo Alto, Puerto Rico. Recruited subjects were randomly assigned to one of three treatment groups: (1) a fluoride-free, alcohol-free mouthwash containing 0.075% CPC (TG); (2) a fluoride-free, alcohol-free mouthwash containing 0.07% CPC (PC); and (3) a fluoride-free, alcohol-free mouthwash without antibacterial agent (NC). Subjects were instructed to rinse with the assigned mouthwash, after tooth brushing, twice daily (morning and evening). After 4 and 6 weeks of product use, subjects were examined for gingivitis (Whole Mouth Gingival, Gingival Interproximal, Gingival Severity Indexes) and plaque (Whole Mouth Plaque, Plaque Interproximal, and Plaque Severity Indexes) parameters. ANCOVA and post hoc Tukey's pair-wise comparisons (α = 0.05) were performed for treatment group comparisons. RESULTS: A total of 132 subjects were screened; 120 were enrolled; and 116 completed the study. After 6 weeks of product use, participants who rinsed with the CPC-containing mouthwashes exhibited statistically significant (P < 0.05) reductions in all the gingivitis and plaque parameters evaluated, whereas in those using the non-antibacterial mouthwash, significant reductions were only observed in whole mouth and interproximal plaque scores. No statistically significant (P > 0.05) differences were observed, with respect to the gingival and plaque parameters, between the two CPC-containing mouthwashes.