Abstract: The antimicrobial effect of the aqueous and ethanolic extracts of Breynia nivosus, Ageratum conyzoides and the combination of herbal preparations on Streptococcus mutans isolated from dental caries patients attending the federal dental clinic Enugu, Nigeria was investigated. The hot water and ethanolic extracts of Breynia nivosus showed zones of inhibition ranging from 10-15 mm at concentrations of 25-400 mg mL-1. The Minimum Inhibition Concentration (MIC) was 25 mg mL-1. All the extracts of Ageratum conyziodes had no inhibitory effect on the test organism. The herbal combinations had 19 mm zone of inhibition at the 400 mg mL-1 concentration of the ethanolic extracts. Phytochemical studies of Breynia nivosus revealed the presence of flavonoids, glycoside, protein, saponnins tannins, carbohydrate, reducing sugar and steroidal aglycone and traces of cardiac glycoside. No clinical signs of acute toxicity were observed in mice given 250-500 mg kg-1 bw of Breynia nivosus extract after 24 h. Histopathological studies of rats fed with 500 and 1000 mg kg-1 bw of Breynia nivosus showed no signs of chronic toxicity as evidenced by the liver and kidney of the rats. This study justifies the use of Breynia nivosus as chewing stick by the people of South- Eastern Nigeria.