Chemotherapeutic mouthrinses are useful adjuncts to normal oral hygiene and regular professional care for patients whose mechanical plaque removal is less than optimal. Recognizing this, the American Dental Association Council on Dental Therapeutics published guidelines for evaluating the safety and efficacy of products for the control of gingivitis. Four 6-month or longer controlled clinical trials have shown Listerine to be significantly effective in helping prevent the development of both supragingival plaque and gingivitis. Two microbiology studies have demonstrated that no resistant microorganisms, opportunistic microorganisms, or presumptive oral pathogens emerge as a result of long-term, daily Listerine use. Listerine is the first nonprescription mouthrinse to receive the Council on Dental Therapeutics Seal of Acceptance as safe and effective in helping to prevent and reduce supragingival plaque accumulation and gingivitis when used in a conscientiously applied program of oral hygiene and regular professional care.