Buccal cells provide a convenient source of DNA for epidemiological studies. The goal of this study was to develop a convenient method to obtain buccal cells from mouthwash samples to be used as a source of DNA, and to evaluate the stability of the DNA in mouthwash solution over time. The procedures used in the method described in this paper avoid the use of any organic solvents. This is achieved by salting out the cellular proteins by dehydration and precipitation with a saturated ammonium acetate solution. The protocol described here is fast, simple to perform, sensitive, economical and several samples can be processed at the same time. The analyses provide consistent evidence that DNA extracted by this methodology is sufficient for several PCR amplifications. The total DNA yield ranged from 5 to 93 µg (median 15 µg, mean 20.71 µg). DNA can be extracted and PCR amplified after storage of mouthwash solution at room temperature for periods of up to 30 days.