T H E C H L O R O M E T H Y L A N A L O G U E of Victamine C,* a cationic surface-active agent, reduces the formation of dental calculus in humans. 1 2 This chemical prevents crystallization of calcium phosphate in calculus smears in vitro, 3 but the mechanism whereby it inhibits calculus formation in vivo is not known. The following study was conducted to determine whether the chloromethyl analogue of Victamine C reduces the formation of dental plaque considered a precursor of calculus. 4 6