Abstract: A class of substituted 1,2,4-triazolo[4,3-]pyridazine derivatives, possessing an optionally substituted cycloalkyl, phenyl or heteroaryl substituent at the 3-position, a substituted alkoxy moiety at the 6-position, and an optionally substituted bicycloalkyl ring system at the 7-position, are selective ligands for GABAA receptors, in particular having high affinity for the &agr;2 and/or &agr;3 subunit thereof, and are accordingly of benefit in the treatment and/or prevention of disorders of the central nervous system, including anxiety and convulsions.