To investigate the effects of carboxylic ester and acid moieties as the N-substituent of opioids, a short series of racemic N-substituted normetazocines was prepared. The introduction of both groups as the normetazocine N-substituent produced compounds which displayed low potency in vitro and in vivo, with the esters displaying the greater activity. The pharmacology of the compounds is discussed with implications resulting from potential in vivo metabolic hydrolysis.