The quantitative determination of acylating agents in non-aqueous media has been demonstrated by the use of4-( p-nitrobenzyl)-pyridine reagent. A thorough investigation was made of acid chlorides, chloroformates, carbamoyl chlorides and anhydrides m methyl ethyl ketone solution. The investigation of 34 acylating agents has shown that the reagent is sensitive to low concentrations of acid chlorides and chloroformates. Other means are necessary to determine low concentrations of carbamoyl chlorides and acid anhydrides. The effects of temperature, molar concentration, amine stabilisers, functional group influence on the acyl carbon and reaction time are discussed.