Aim: To evaluate the effect of different mouth rinses 12 h after rinsing on genuine intra-oral halitosis. Materials and Methods: Twenty-four adults with halitosis were included in a double-blind, crossover, randomized clinical trial. Halitosis was evaluated 12 h after rinsing with placebo and five mouth rinse products containing zinc acetate and chlorhexidine diacetate; zinc lactate, chlorhexidine and cetylpyridinium chloride; zinc acetate and chlorhexidine diacetate with reduced amounts of mint and menthol; zinc chloride and essential oil; and chlorine dioxide using the organoleptic method and a gas chromatograph. Test periods were separated by 1 week. Results: Hydrogen sulphide (H2S), methyl mercaptan (MM) and the organoleptic scores (OLS) were significantly reduced 12 h following rinsing with all substances compared to placebo (P < 0.05). H2S was more effectively reduced after rinsing with zinc acetate and chlorhexidine diacetate and zinc acetate and chlorhexidine diacetate with reduced amounts of mint and menthol compared to rinsing with zinc chloride and essential oil (P < 0.05), and significantly lower values of MM were obtained after rinsing with zinc acetate and chlorhexidine diacetate compared to zinc lactate, chlorhexidine and cetylpyridinium chloride (P < 0.05). The percentage effectively treated individuals (H2S (<112 ppb), MM (<26 ppb) and OLS score <2) varied from 58% percentage (zinc acetate and chlorhexidine diacetate) to 26% (zinc chloride and essential oil). Conclusion: All treatments resulted in reduction in halitosis 12 h after rinsing compared to placebo. H2S and MM were most effectively reduced by zinc acetate and chlorhexidine diacetate.