A class of 8-fluoro-3-phenylimidazo[1,2-.alpha.]pyridine derivatives, substituted at the meta position of the phenyl ring by an optionally substituted aryl or heteroaryl group, or by a pyrrolidinonyl group, which is directly attached or bridged by an oxygen atom or by a --NH-- or --OCH.sub.2-- linkage, being selective ligands for GABA.sub.A receptors, in particular having high affinity for the .alpha.2 and/or .alpha.3 and/or .alpha.5 subunit thereof, are accordingly of benefit in the treatment and/or prevention of adverse conditions of the central nervous system, including anxiety, convulsions and cognitive disorders.