Some confusion exists in the literature whether correlations exist between gingivitis severity and plaque levels as measured by the corresponding indices. The results of a clinical trial and a re-analysis of literature data indicate that a strong statistical correlation exists between the Löe-Silness Gingival Index values and both the Löe and the Quigley-Hein Plaque Index measurements. Furthermore, regression analyses also indicate that Löe-Silness Gingival Index can be expressed as linear functions of either the Löe Plaque Index or the Quigley-Hein Plaque Index and that for each unit increment in the mean plaque index values a half unit increase in the gingival index value can be expected.