Rinsing the mouth with water is recommended to remove inhaled corticosteroid (ICS) deposited on the oropharyngeal mucosa. Given the lipophilicity of fluticasone propionate (FP), an ethanol-based mouthwash was hypothesized to be superior to water. This study's purpose was to compare the effectiveness of water versus Listerine (Warner Lambert, Lititz, PA) in removing FP from the oropharyngeal mucosa. Asthma patients were randomly assigned water or a Listerine-rinsing vehicle. A 440-microgram dose of FP was inhaled. After the second puff, patients rinsed for 30 seconds with 20 mL of the assigned agent and then repeated the process, spitting each "wash" into the same cup. At visit 2, patients used the alternate vehicle and repeated the procedure. Samples were frozen until analyzed using liquid chromatography/mass spectrophotometry (lower limit of detection 0.067 microgram/mL). Thirty-six patients (mean age, 44 years; 66% female) participated. Mean inhaler technique score was 11.3 (scale of 1-12). Eighty-three percent used the closed-mouth technique. The mean concentration of FP removed by Listerine was not statistically different than that removed by water, 1.67 micrograms/mL (range, 0.067-4.195 micrograms/mL) and 1.42 micrograms/mL (range, 0.067-5.107 micrograms/mL), respectively, and the total milliliter returned was assumed to be 40 mL. Regression analysis using sex, age, and inhaler technique showed no statistical relationship with the amount of FP removed. Therefore, Listerine was not more effective than water in removing FP from the oropharyngeal mucosa (p = 0.53). Thus, water is an adequate rinsing vehicle for removal of ICS deposited on the oropharyngeal mucosa. Other factors besides the rinsing vehicle are strong factors in determining the amount of drug removed.