Acesulfam K (AK) is a non-sucrose sweetener developed by Hoechst Corporation. According to its manufacturer it is 300-350 times as sweet as sucrose. Because of its potential use as a sucrose substitute by individual and industrial consumers, its cariogenic potential was investigated. The experiment consisted of three groups of rats (l0/group) which were fed one of the following diets: Group One (Suc) -NIH Diet 2000 (56 percent sucrose); Group Two (AK) -NIH Diet 2114 (56 percent raw corn starch) plus 5 percent Acesulfam K; Group Three (RCS) Diet 2114 (56 percent raw corn starch). The experiment was performed using a Konig-Hofer progammable feeding machine which delivered 17 meals/17 hour period of the assigned diets. An additional 12 meals of diet 2114 was provided all three groups as a supplement. All animals were initially infected with S. mutans 6715. Oral infection levels were determined twice weekly. After 56 experimental days the rats were sacrificed. Mean smooth surface caries scores for the three groups were: Suc=13.4; AK=0; and RCS=5.9. It appears that AK has a low cariogenic potential in rats.