Aqueous extracts, 1% (w/v), of Nigerian chewing sticks derived from the African plants Serindeia warnecki, Prosopsis africana, Pseudocedrela kotschyi, and Anoigeissus schrimperi were found to effectively inhibit the attachment of S. mutans 6715wt13 to glass or saliva-coated hydroxy-apatite beads. It was shown that the active compounds in these extracts interfere with binding of the bacteria, resulting in reduced adherence. Although no large effect upon the total extracellular glucan synthesis was noted, there was a 15% reduction in the water-insoluble polysaccharide synthesis. Chemical and spectral analysis of the active constituent from S. warnecki showed this material to have the characteristics of a high molecular weight polyphenolic tannin. 1% aqueous solution of tannic acid was also shown to promote similar in vitro adherence inhibition as the tannin-like substance from S. warnecki. In conclusion, the results imply that chewing stick constituents appear to play an important role in restricting plaque accumulation and caries incidence.