During the study of various kinds of prostaglandin derivatives, it has been found that there exist many prostaglandins having the prostanoic acid skeletone in which has at least one halogen atom, especially fluorine atom, at the 16- or 17- position [16(17)-mono or 16,16 (17,17)-dihalo-prostaglandins] represented by the following formula: ##STR1## that exhibit characteristic pharmacological activit