The synthesis of a series of 6-(substituted-phenyl)-l, 2, 4-triazolo [4, 3-b] pyridazines (VIII) is reported. Some of these derivatives show activity in tests predictive of anxiolytic activity [(a) protection against pentylenetetrazole-induced convulsions;(b) thirsty rat conflict procedure]. They also represent a new class of compound which inhibits [3H] diazepam binding. Structureactivity correlations, as well as the ability of structures VI11 to inhibit [3 H] diaze~ ...