The preparation of 5-substituted 1-aryl-4,5-dihydro-1H-pyrazolo[4,3- c][1,8] naphthyridines by reaction of 5-substituted 3-hydroxymethylene-2,3-dihydro-1,8-naphthyridin-4(1H)-ones with various phenylhydrazines is described. The benzodiazepine binding activity of these compounds was evaluated in vitro. Only the 5-methyl substituted derivatives showed affinity for the benzodiazepine receptor, with K1 values ranging from 2.9 to 0.195 microM for the para-phenyl substituted compounds. A hypothesis of interaction of these ligands with the receptor site is reported.