Abstract: N-Phenyl-N', N'-diethylethylenediamine and N-(p-nitrophenyl)-N', N'-diethylethylene-diamine were acylated with propionic anhydride, phenylacetic anhydride or p-ethoxy-phenylacetic anhydride respectively, giving a series of N-aryl-N-acyl-N', N'-diethylethy-lenediamines (Ⅳ_a-e). These compounds were synthesized in imitation of the benzoimidazoles which were reported by Hunger et al. to be strong analgesics. Pharmacological examinations revealed that these compounds were devoid of pronounced analgesic activity.