Prostaglandin E.sub.1 analogues of the general formula: ##STR1## [wherein Y represents ethylene or trans-vinylene, Z represents ethylene or trans-vinylene, R.sup.1 represents a hydrogen atom, an alkyl group containing from 1 to 12 carbon atoms, an aralkyl group containing from 7 to 12 carbon atoms, a cycloalkyl group containing from 4 to 7 carbon atoms and unsubstituted or substituted by at least one alkyl group containing from 1 to 6 carbon atoms, a phenyl group unsubstituted or substituted by at least one chlorine atom, trifluoromethyl group, alkyl group containing from 1 to 4 carbon atoms or phenyl group, a --C.sub.m H.sub.2m COOR.sup.5 group (wherein m represents an integer of from 1 to 12 and R.sup.5 represents a hydrogen atom or an alkyl group containing from 1 to 4 carbon atoms), a --C.sub.n H.sub.2n OR.sup.6 group (wherein R.sup.6 represents a hydrogen atom or an alkyl group containing from 1 to 4 carbon atoms and n represents an integer of from 2 to 12), or a ##STR2## group (wherein R.sup.7 and R.sup.8 each represent a hydrogen atom or an alkyl group containing from 1 to 4 carbon atoms and n is as hereinbefore defined), R.sup.2 represents a hydrogen atom or a methyl or ethyl group, R.sup.3 represents a single bond or an alkylene group containing from 1 to 4 carbon atoms, R.sup.4 represents a hydrogen atom, an alkyl group containing from 1 to 8 carbon atoms, a cycloalkyl group containing from 4 to 7 carbon atoms and unsubstituted or substituted by at least one alkyl group containing from 1 to 8 carbon atoms, or represents a phenyl or phenoxy group unsubstituted or substituted by at least one chlorine atom, trifluoromethyl group or alkyl group containing from 1 to 3 carbon atoms, and the wavy line attached to the C-11 and C-15 carbon atoms represents .alpha.- or .beta.- configuration or mixtures thereof] and cyclodextrin clathrates thereof, and, when R.sup.1 represents a hydrogen atom or a group C.sub.m H.sub.2m COOR.sup.5 in which R.sup.5 represents a hydrogen atom, non-toxic salts thereof and, when R.sup.1 represents a group ##STR3## non-toxic acid addition salts thereof, are new compounds and possess characteristic prostaglandin-like properties.