The present invention provides a composition comprising an HFO compound, the composition having excellent stability with decomposition and oxidation of the HFO compound being inhibited, the composition having improved refrigerating capacity when used as a heat transfer medium, compared with the case in which an HFO compound is used alone. More specifically, the present invention provides a composition comprising at least one HFO compound selected from the group consisting of HFO-1234yf, (E-/Z-)HFO-1234ze, and (E-/Z-)HFO-1225ye; and a chlorine-containing compound, wherein (1) the chlorine-containing compound is at least one member selected from the group consisting of CH.sub.2=CHCl, CHF=CHCl, CH.sub.2=CFCl, CF.sub.3Cl, CH.sub.3Cl, CF.sub.3CH.sub.2Cl, CClF=CHCl, and CHF=CCl.sub.2, and (2) the chlorine-containing compound is contained in an amount ranging from 1 to 500000 mass ppm.

The present invention provides a composition comprising an HFO compound, the composition having excellent stability with decomposition and oxidation of the HFO compound being inhibited, the composition having improved refrigerating capacity when used as a heat transfer medium, compared with the case in which an HFO compound is used alone. More specifically, the present invention provides a composition comprising at least one HFO compound selected from the group consisting of HFO-1234yf, (E-/Z-)HFO-1234ze, and (E-/Z-)HFO-1225ye; and a chlorine-containing compound, wherein (1) the chlorine-containing compound is at least one member selected from the group consisting of CH.sub.2=CHCl, CHF=CHCl, CH.sub.2=CFCl, CF.sub.3Cl, CH.sub.3Cl, CF.sub.3CH.sub.2Cl, CClF=CHCl, and CHF=CCl.sub.2, and (2) the chlorine-containing compound is contained in an amount ranging from 1 to 500000 mass ppm.