Extensive testing for the safety of the GK-101 solution was conducted with experimental animals. An Investigational New Drug permit was awarded by the Food and Drug Administration before clinical studies. Subsequently, two studies--one double-blind and one open--were conducted to determine the safety and caries-removing efficacy of a 0.05% solution of N-monochloroglycine (GK-101) on clinical subjects, as well as to study the technique for such a procedure. In the double-blind study, the efficacy, as shown by ratings for caries removal, of GK-101 applied under pressure was significantly greater than that of the placebo solution of normal saline (P less than 0.01). Both treatment groups were comparable with respect to the age distribution, pretreatment intraoral examination results, and past history. No drug-related reactions were reported by patients in either group. On the basis of caries removal results in the open study, GK-101 solution, in conjunction with the pump system, was found to be effective as determined by the investigator. The caries in all but one of the 61 lesions treated with GK-101 was rated as "total removal" or as "almost total to total" removal. Approximately 77% of the patients treated with GK-101 experienced neither pain nor an odd taste. Any pain reported was always described as "slight" or "little." The drug is currently being further tested for safety and efficacy.