Abstract: The invention concerns a heterocyclic cycloalkane of the formula I ##STR1## wherein Q is an optionally substituted 6-membered monocyclic or 10-membered bicyclic heterocyclic moiety containing one or two nitrogen atoms;A is (1-6C)alkylene, (3-6C)alkenylene, (3-6C)alkynylene or cyclo(3-6C)alkylene;X is oxy, thio, sulphinyl, sulphonyl or imino;Ar is phenylene which may optionally bear one or two substituents orAr is an optionally substituted 6-membered heterocyclene moiety containing up to three nitrogen atoms; R.sup.1 is hydrogen, (1-6C)alkyl, (3-6C)alkenyl, (3-6C)alkynyl, cyano-(1-4C)alkyl or (2-4C)alkanoyl, or optionally substituted benzoyl; and R.sup.2 and R.sup.3 together form a (3-6C)alkylene group which, together with the carbon atom to which R.sup.2 and R.sup.3 are attached, defines a ring having 4 to 7 ring atoms, and which ring may bear one or two substituents; or a pharmaceutically-acceptable salt thereof.The compounds of the invention are inhibitors of the enzyme 5-lipoxygenase.