The use of Strychnos afzelii GILG (Loganiaceae) stem as chewing stick have been reported by several authors [I]. Extracts of the stem bark were found to exhibit antimicrobial activity, among others against Streptococcus species connected with caries. In the extracts the alkaloids bisnor-dihydrotoxiferine (I), bisnor-C-alkaloid H (11), caracurine V (IV) and WIELAND-GUM-LICH aldehyde (V) were identified. The tertiary dimeric indole alkaloids I, I1 and IV were found to be responsible for the antimicrobial effect.