To compare the cleaning efficacy of (A): a newly developed manual toothbrush with tapered filaments (meridol®, GABA International, CH-Münchenstein) with (B): a standard flat trim manual toothbrush (ADA reference toothbrush) in vivo. 87 healthy participants took part in this study. Subjects were asked to abstain from all oral hygiene procedures for 48 hours. After plaque was scored (Turesky modification of the Quigley Hein Index), the subjects brushed their teeth under supervision with the two manual toothbrushes according to a split-mouth design. In total, a cleaning time of two minutes was given for the whole procedure with an alert after every 30 seconds. Immediately after brushing, plaque was scored again by the same investigator, who was blind with respect to the toothbrush used. Using the non-parametric Wilcoxon test for paired samples (p0.05) the overall plaque scores were reduced for (A) from 1.95±0.48 to 1.02±0.41 (p0.001), and (B) from 1.93±0.52 to 1.09±0.44 (p0.001). At proximal surfaces the plaque scores were reduced (A) from 2.02±0.49 to 1.11±0.43 (p0.001) and (B) from 2.01±0.52 to 1.20±0.45 (p0.001). The relative plaque reductions overall were (A) 47.4±18.0% and (B) 44.1±15.6% (p=0.039), at proximal surfaces (A) 44.2±18.8% and (B) 40.5±15.9% (p=0.015), and at lingual surfaces (A) 30.6±28.1% and (B) 24.0±27.1% (p=0.016). Both brushes removed a significant amount of plaque. Overall and in areas difficult to reach, the meridol® toothbrush was superior to the ADA reference brush. Keywords: manual toothbrush, plaque removal, mechanical plaque control, controlled clinical trial