Objective: This 6-month, examiner-blind, single-center, randomized, parallel group clinical trial compared the antiplaque and antigingivitis effects of an essential oil-containing mouthrinse with zinc chloride and sodium fluoride (EO) to a 0.05% cetylpyridinium chloride-containing mouthrinse (CPC) also with fluoride. Method and Materials: Four hundred and eight gingivitis subjects were monitored for the primary outcomes of modified Gingival Index (MGI) and Plaque Index (PI) at baseline and 3 and 6 months. Subjects were randomly assigned to 6-month twice a day unsupervised use of EO, CPC, or negative control rinse in conjunction with normal brushing and flossing. Results: EO was always better than CPC at 3 and 6 months considering all parameters. All benefits allowed by EO increased from 3 to 6 months. CPC was better than the negative control at 3 and 6 months with respect to whole mouth plaque, and the proportion of more severe sites (baseline scores > 3) in PI and MGI. At 6 months, CPC did not differ from negative control in relation to whole mouth MGI reduction, proximal MGI reduction, and percentages of sites improved over baseline in PI and MGI. Conclusion: This new EO mouthrinse provided superior clinical benefits to CPC and demonstrated increasing plaque and gingivitis reductions over 6 months. Our findings support the regular long-term use of the EO mouthrinse and selection over a 0.05% CPC rinse for better efficacy. Keywords: cetylpyridinium chloride, clinical trials, essential oil, gingivitis, mouthrinse