Purpose: The purpose of this cross-over, double-blind, placebo-controlled, randomised in situ study was to evaluate the remineralisation of demineralised enamel specimens using a CHX/NaF mouthrinse in comparison with a CHX- and a placebomouthrinse. Materials and Methods: Twenty-four volunteers received intraoral appliances with mounted demineralised enamel specimens. They rinsed their mouths twice a day (10 ml for 1 minute) with the respective preparation. After 14 days, the in situ mineral gain and fluoride uptake were determined. Results: Mineral gain was significantly higher after using CHX/F mouthrinse (358.4 ± 372.1 Vol.%·µm) compared with CHX (95.6 ± 192.2 Vol.%·µm) and placebo treatment (80.8 ± 159.6 Vol.%·µm). Moreover, CHX/F treatment (2751.1 ± 1494.9 µg/cm3) resulted in a significantly higher fluoride uptake compared with CHX- (83.8 ± 94.0 µg/cm3) and placebo- (136.6 ± 137.3 µg/cm3) mouthrinses. Conclusion: The in situ study approves that using a CHX/F mouthrinse supports the remineralisation of initial carious lesions. Palabras clave: caries, chlorhexidine, enamel, mouthrinse