Purpose: The in-situ efficacy of an experimental stannous (Sn)-containing sodium fluoride (NaF) dentifrice against erosion and erosive tooth wear was compared with a conventional NaF dentifrice. Materials and Methods: This was a randomised, controlled, double-blind, parallel-group clinical trial. Mandibular appliances containing four enamel specimens (2 per side [L/R] of the appliance) were worn by 60 generally healthy adult subjects. Subjects were randomised to treatment based on age and gender. Treatments included a Sn-containing NaF or conventional NaF dentifrice. Conditions of erosion (dentifrice slurry treatment) and erosion/tooth wear (dentifrice slurry plus brushing) were compared. Dentifrices were used twice per day for 30 s of lingual brushing, followed by 90 s of slurry exposure. In addition, the two specimens on the left side of the mouth were brushed for 5 s each, using a power toothbrush. All specimens were exposed to four daily erosive challenges with commercial orange juice (pH 3.6). Tooth wear was measured as enamel loss using non-contact profilometry on day 10. Results: At the day 10 visit, the adjusted mean (SE) enamel loss for specimens receiving slurry (erosion) treatment was 4.7 µm (0.61) [Sn-containing NaF] and 8.73 µm (1.12) [NaF control], with results demonstrating a statistically significant benefit for the Sn-containing dentifrice (46.2% benefit; p = 0.009). For specimens exposed to erosion/tooth wear conditions, enamel loss = 6.68 µm (1.29) (Sn-containing NaF) and 10.99 µm (1.29) (NaF group), with results statistically significant (p = 0.048; 39.2% better, favouring the Sn-containing dentifrice). When data were combined, enamel loss (SE) for all specimens subjected to erosion + erosion/tooth wear was 5.61 µm (0.77) (Sn-containing NaF]) and 9.9 µm (1.3) (NaF group). The difference again was statistically significant, favouring the Sn-containing group (p = 0.022; 43.4% better). Conclusions: The Sn-containing dentifrice demonstrated significantly better protection than did NaF under erosive and erosive/tooth wear conditions. Schlagwörter: dental erosion, dentifrice, erosive tooth wear, in situ clinical, stannous fluoride