A randomized, double-blind, placebo-controlled study evaluated the effectiveness of a new and improved prebrushing dental rinse, Advanced Formula Plax, in reducing supragingival plaque. Following a 4-week pretest phase, the oral soft tissue, stain, gingivitis, and pre- and postbrushing plaque scores were evaluated for 153 subjects at baseline, 6, 12, 18, and 26 weeks. Patients were randomly assigned to receive either the active prebrushing dental rinse or a matching placebo that lacked the key ingredients responsible for the surfactant action of the active rinse. Compared with placebo, use of the active prebrushing rinse was associated with a significant reduction from baseline in postbrushing plaque scores at 12, 18, and 26 weeks on smooth surfaces, and with a significant reduction in postbrushing plaque scores on all surfaces at weeks 18 and 26. No significant difference was noted between the two treatment groups in gingivitis scores and stain indices. No product-related adverse experiences were noted. The results indicate that use of the new and improved prebrushing dental rinse represents a beneficial adjunct to toothbrushing and improved oral hygiene.