Objective: To determine the effectiveness of a denture cleanser in reducing the concentration of volatile sulphur compounds (VSC) and its antimicrobial action. Background: Micro-organisms from the denture biofilm can cause local and systemic disease and halitosis. Denture cleansers are important adjuncts in oral care, but there is limited investigation on their effect in malodour compounds. Material and methods: Nineteen institutionalised elderly who wore at least an upper denture were selected; their VSC concentrations were measured and the denture biofilm was collected. In phase 1, the subjects wore their old denture and data were collected before (B(0)) and after 7(A(1)), 14(A(2)), 28(A(3)) days of continuous daily use of the denture cleanser. In phase 2, new dentures were inserted and measurements were made at 30(A(1.1)), 60(A(2.2)), 90(A(3.3)) days of treatment. Results: The VSC concentration increased from B(0) to A(1) (p < 0.05)(,) but no differences were found for the others intervals of times. Total micro-organism data did not show a statistical difference between times in Phase I, but in Phase II, there was a statistical difference (p < 0.05) and a progressive re-colonisation was observed. Conclusion: Within the limits of this study, it was concluded that the denture cleanser had no antimicrobial effect and VSC levels were not reduced.282134139