Rate coefficients and product branching fractions have been determined for 31 ion-molecule reactions involving PF5 or PF5-. About half of the reactions studied show an ion-molecule association channel. NH2- and OH- reaction with PF5 yields HF product. F- and electron transfer channels are also observed in many of the reactions studied. Consideration of the efficiency of the electron transfer channel in these reactions leads to the conclusion that the adiabatic electron affinity of PF5 is 0.75 +/- 0.15 eV.