The composition comprises certain 5-acylsalicylanilides and more particularly comprises the compounds encompassed by the following generic formula: ##STR1## Where Z is a substituted phenyl ring of from 6 to 30 carbon atoms including substituents, R is a substituted or unsubstituted alkyl or phenyl group of from 2 to 30 carbon atoms including substituents and M is a radical selected from the group consisting of --C.dbd.N,--F,--NO.sub.2,--H, lower alkyl or lower haloalkyl.The preferred compositions of the invention have a partition coefficient greater than 4 and the substituted moieties in the phenyl ring of the Z group have a combined overall electron withdrawing effect on the phenyl ring of the Z group.The method of the invention comprises contacting the microorganism with a sufficient concentration of the above composition for a sufficient time to inhibit the growth of the microorganism.The above compositions are effective antiseptics against a wide range of microorganisms, especially bacteria, and the compositions surprisingly are especially effective against microorganisms prevalent in dental plaque.