Ab initio calculations have been performed to examine the properties of the protonated fluoroform cation (CF3H2+). These calculations show that the global minimum for CF3H2+ is [CF2H ... FH](+) among three possible configurational isomers. This isomer is suggested to be an ion-dipole complex between CF2H+ and FH. The barrier to internal rotation of the bond between carbon of CF2H+ and fluorine of HF is calculated as 0.96 kcal mol(-1) at the MP2/6-31G(d,p) level of theory. The heat of formation of CF3H2+ at 298.15 K is estimated to be 60.6 kcal mol(-1) from the G2 calculation. (C) 1998 Elsevier Science B.V.