Phenylpiperazine derivatives of formula (I): ##STR1## where R.sup.1 is benzyl, C.sub.1-6 alkyl or optionally substituted phenyl; R.sup.2 is optionally substituted phenyl; R.sup.3 is hydrogen or C.sub.1-4 alkyl; Q is furan, thiophene, oxazole or thiazole; m is 1 to 3 and n is 0 or 1; and pharmaceutically-acceptable salts thereof are active in the chemotherapy of immediate hypersensitivity conditions such as asthma.