Using an experimental gingivitis model, 99 subjects completed a 3-week study to determine the correlations between a visual index of gingivitis, the Modified Gingival Index (MGI), and the Gingival Index (GI), the Interdental Bleeding Index (IBI), and the Papillary Bleeding Index (PBI). Following a baseline examination consisting of the MGI and either the GI, IBI, or PBI, each subject received a full mouth scaling and rubber cup polishing to render the teeth plaque and calculus free. Subjects then rinsed twice daily for 30 seconds with 20 ml of either an active antimicrobial or control mouthrinse for 3 weeks while abstaining from all other oral hygiene. The MGI correlated significantly with the GI, IBI, and PBI, both at baseline and at 3 weeks for all subjects.