Isoproterenol has been reported to alter salivary gland development in the rat. Because salivary glands and the in rats saliva they produce play an important role in the etiology of dental caries, the effect of this pharmacologic agent on the caries process was investigated. Rat pups born to and suckled by dams fed isocaloric 8 or 25% protein diets were injected intraperitoneally with either 16 mg/kg isoproterenol or isotonic saline from day 6 to 16. From weaning on, all pups were fed a caries-promoting diet. Caries scores for molars from rats treated with isoproterenol were higher than those of control rats. It is concluded that isoproterenol administration to suckling rats during development of salivary glands induced changes which resulted in an increased dental caries susceptibility regardless of nutritional status.