Although the efficacy of chlorhexidine (CHX) chemically can be affected by the presence of a sodium lauryl sulphate (SLS)-containing dentifrice in the oral cavity, previous data, collected without supervision, showed that the level of plaque inhibition offered by a 0.2% CHX post-brushing rinse in one jaw is not reduced under the influence of toothbrushing with a 1.5% SLS-containing dentifrice in the opposite jaw. The aim of the present study was to investigate, during a 4-day supervised study period, the anti-plaque efficacy of a 0.2% CHX pre-brushing rinse in one jaw, under the influence of toothbrushing in the opposite jaw, either with a SLS-containing dentifrice or with a SLS-free dentifrice. Three different dentifrices were tested. Two of them contained SLS (Colgate Total & Aquafresh Natural Whitening), the other (Zendium) did not. The study was an examiner blind, randomised 4-cell, crossover design. It used a 4-day plaque accumulation model to compare under supervision 4 different oral hygiene regimens with a washout period of at least one week. Thirty-five healthy volunteers were enrolled in the study and were randomly assigned to a sequence according to a 4 x 4 Latin square design. At the beginning of each 4-day test period, they received a thorough dental prophylaxis. Plaque was scored in one randomly assigned (upper or lower) jaw, called the study jaw. At the end of the 4-day period the study jaw was used to study the effect of the four regimens on the level of plaque accumulation. The opposite jaw was assigned as the dentifrice jaw and served only to introduce the effect of brushing with a dentifrice in the study model. Four oral hygiene regimens were designed. During the randomly assigned test periods, rinsing with 0.2% CHX and then brushing the dentifrice jaw was performed twice daily. In regimen 1, 2, and 3 the subjects used a dentifrice in the assigned dentifrice jaw being either a dentifrice with SLS (Colgate Total and Aquafresh Natural Whitening) or a SLS-free dentifrice (Zendium). Regimen 4 served as a control during witch subjects only rinsed with 0.2% CHX. No other oral hygiene methods were allowed. After 4 days of undisturbed plaque accumulation, the amount of plaque was evaluated (Lobene et al. 1982, Quigley & Hein 1962, Turesky et al. 1970 modifications). The overall plaque index for regimen 1, 2 and 3 was, respectively, 1.8, 1.8 and 1.9. For regimen 4, the overall plaque index was 1.9. There was no significant difference in plaque accumulation between the four regimens. Within the present study design, it can be concluded that the anti-plaque efficacy of a pre-brushing 0.2% CHX mouthrinse does not seem to be reduced under the influence of a normal toothbrushing exercise with a dentifrice after rinsing, whether the dentifrice contains SLS or not.