Stannous fluoride (SnF2) is a broad-spectrum antimicrobial agent effective against caries, plaque, and gingivitis. Because oral malodor has a microbial etiology, the potential immediate effects of SnF2 on malodor were evaluated in 2 independent, randomized clinical trials. Both studies used a similar double-blind, crossover design, with subjects randomized to a treatment sequence with a 0.454% stabilized SnF2 sodium hexametaphosphate dentifrice or sodium fluoride dentifrice control. Overnight malodor was assessed at baseline in the morning before brushing and 24 hours later, after morning and evening brushing with the assigned product. In the first study, volatile sulfur compounds (VSC) were measured instrumentally via a portable sulfide monitor (Halimeter) with an electrochemical gas sensor. The second study used second-person malodor assessment on a 9-point hedonic scale. Treatments were compared at each time point using analysis of variance for crossover designs. Seventy-five subjects completed the evaluation (26 in the first and 49 in the second clinical trial). The use of the stabilized SnF2 dentifrice resulted in statistically significant reduction of overnight VSC (P <.03) and the overnight hedonic scores (P <.02) relative to the negative control after 1 day of product use. These 2 randomized, controlled clinical trials provide evidence of significant immediate malodor activity for a 0.454% stabilized SnF2 sodium hexametaphosphate dentifrice.