Compressed CO2 gas (1-94 bar) depresses both the crystallisation temperature (T-c) and the melting temperature (T-m) of isotactic polypropene (iPP). The T-c of CO2-treated iPP decreases linearly with a dT(c)/dP value of --0.18 K/bar. Similar to T-c, the T-m, of CO2-treated iPP decreases linearly with a dT(c)/dP value of -0.18 K/bar. Experimental Delta T-m (= T-m - T-m＇) values, where T-m＇ is the melting temperature at a CO2 pressure of 1 bar, coincide with those predicted on the basis of the Flory-Huggins theory. (C) 2000