Abstract: Prostaglandin analogues of the general formula: ##STR1## (wherein R.sup.1 represents a hydrogen atom or a straight- or branched-chain alkyl group, Y.sup.1 represents a carbonyl or hydroxymethylene group, represents a single or double bond, A.sup.1 represents an alkylene linkage containing 2 or 3 carbon atoms and optionally bearing a methyl or ethyl substituent, R.sup.2 represents a hydrogen atom or a methyl or ethyl group and R.sup.3 represents a hydrogen atom or else R.sup.2 and R.sup.3 form an alkylene linkage containing 2 or 3 carbon atoms, optionally bearing a methyl or ethyl substituent, such that the symbols A.sup.1, R.sup.2 and R.sup.3, together with the carbon atoms through which they are connected, form a cycloalkyl ring of 6, 7 or 8 carbon atoms, optionally bearing one or two methyl or ethyl substituents, X.sup.1 represents an ethylene or trans-vinylene group, Y.sup.2 represents a carbonyl or hydroxymethylene group, and either (i) A.sup.