Prostaglandin analogues of the general formula: STR1 [wherein the ring A represents: STR2 the ring B represents: STR3 (wherein R6 represents hydrogen, methyl or ethyl, and r is zero, one or two), Y represents ethylene, cis- or trans-vinylene or ethynylene, Z represents a grouping of the formula: --(CH2)m --, --(CH2)3 --CHR7 --, --(CH2)2 --CHR7 --CH2 --, --CH2 --CHR7 --(CH2)2 --, --CHR7 --(CH2)3 --, or trans--(CH2)2 --CH=CH-- (wherein m is 3, 4 or 5, and R7 represents methyl or ethyl), R1 represents a grouping of the formula: --COOR8, STR4 or --CH2 OR11 (wherein R8 represents hydrogen, alkyl, aralkyl, cycloalkyl which is unsubstituted or substituted by at least one alkyl group, or R8 represents phenyl which is unsubstituted or substituted by halogen, trifluoromethyl, alkyl, alkoxy, alkylthio or phenyl, or represents naphthyl, 2,3- or 1,3-dihydroxypropyl, 2,3- or 1,3-bisalkanoyloxypropyl, a grouping of the formula: -D1 --COOR12, STR5 -D2 -R15 or -D3 -R16, wherein D1 represents alkylene, D2 represents alkylene, D3 represents a single bond or alkylene, R12, R13 and R14, each represent alkyl, R15 represents hydroxy, alkoxy or alkylthio and R16 represents a heterocyclic ring, or R8 represents a grouping of the formula: STR6 R9 and R10, each represent hydrogen, alkyl, alkylsulphonyl, alkanoyl or STR7 represents a heterocyclic ring, and R11 represents hydrogen or alkanoyl, R2 represents hydrogen, methyl or ethyl, R3 represents a single bond or alkylene, R4 represents hydrogen, alkyl, alkoxy, cycloalkyl or cycloalkyloxy unsubstituted or substituted by alkyl, or represents phenyl or phenoxy unsubstituted or substituted by halogen, trifluoromethyl or alkyl with the proviso that, when R3 represents a single bond, R4 does not represent alkoxy, cycloalkyloxy or phenoxy, R5 represents hydrogen, methyl or ethyl and with the proviso that, when one of the groups R5, R6 and R7 represents methyl or ethyl the other two groups are hydrogen atoms] and cyclodextrin clathrates, non-toxic salts and non-toxic acid addition salts thereof, possess selective strong stimulatory activity on uterine contraction in female mammals.