Male and female rats and rabbits were used in this study to investigate the acute and subchronic toxicity of a new antismoking (A.S.) mouth wash (0.5% silver nitrate as the active ingredient). The LD50 values for i.p. administration in male and female rats were 35.7 and 37.2 mg/kg body weight, respectively. The corresponding values in male and female rabbits were 113 and 128 mg/kg body weight, respectively. The oral LD50 values of the mouthwash in male and female rats were 428 and 433 mg/kg body weight, respectively. The corresponding values in male and female rabbits were 1261 and 1320 mg/kg body weight, respectively. Postmortem and histopathological examination revealed congestion, edema, hemorrhage, and mucosal necrosis with brown pigment deposition in the upper gastrointestinal and respiratory tracts for the orally treated animals and ascitis, peritoneal fat necrosis, and pigment deposition in i.p. administered animals. Subchronic toxicity involved administration of low (1.5 mg/kg), intermediate (15 mg/kg), and high (150 mg/kg) doses of A.S. mouthwash by swabbing the oral cavity daily for 30 consecutive days. Body weight, hematologic observations, and histopathological examination showed no significant differences between control and treated animals, except for dark coloration in teeth and increased platelet counts in treated rats.