Abstract: A class of substituted piperidine and tetrahydropyridine derivatives, linked through the 4-position thereof via an alkylene chain to a fused bicyclic heteroaromatic moiety such as indolyl, and further substituted at the 1-position by an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl-alkyl, aryl-alkyl or heteroaryl-alkyl moiety, are selective agonists of 5-HT.sub.1 -like receptors, being potent agonists of the human 5-HT.sub.1D.spsb..alpha. receptor subtype whilst processing at least a 10-fold selective affinity for the 5-HT.sub.1D.spsb..alpha. receptor subtype relative to the 5-HT.sub.1D.spsb..beta. subtype; they are therefore useful in the treatment and/or prevention of clinical conditions, in particular migraine and associated disorders, for which a subtype-selective agonist of 5-HT.sub.1D receptors is indicated, whilst eliciting fewer side-effects, notably adverse cardiovascular events, than those associated with non-subtype-selective 5-HT.sub.1D receptor agonists.