Calculations of the rate constant at several temperatures for the reaction C+(2P)+HCl(X 1∑+) are presented. A quantum mechanical treatment of ion–molecule reactions which combines a rotationally adiabatic capture with a centrifugal sudden approximation is used to obtain rotational state-selective cross sections and rate constants. Ab initio SCF (TZ2P) methods are employed to obtain the long- and short-range electronic potential energy surfaces. This study indicates the necessity of incorporating the multisurface nature of open-shell systems for some ion–molecule reactions. The spin–orbit interactions are treated within a semiquantitative model. Results fare better than previous calculations which used only classical electrostatic forces, and are in good agreement with CRESU and SIFT measurements at 27, 68, and 300 K.