Abstract: The fat emulsions containing the prostaglandin I.sub.2 's expressed by the following formula (I): ##STR1## where X represents an oxygen atom to a methine group, Y is a carbon atom, Z represents a methylene or methine group; when X is an oxygen atom, the mode of Y-Z binding is a double bond of carbon-carbon, and when X is a methine group, the mode of X-Y binding is a double bond of carbon-carbon and Z is a methylene group; R.sub.1 represents a hydrogen atom or alkyl group, R.sub.2 represents a hydrogen atom or fluorine atom, and R.sub.3 represents a hydrogen atom, methyl group, ethyl group or vinyl group. R.sub.4 represents a substituted or unsubstituted alkyl group with 1-10 carbon atoms, a substituted or unsubstituted alkenyl group with 2-10 carbons atoms, a substituted or unsubstituted alkynyl group with 2-10 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-8 carbon atoms; and n is zero (0) or an integer of value 1.