The selectivity of the vibrational and rotational states of products in the gas-phase proton-transfer reaction F- + HCl (X(1) Sigma(+)) --> HF(nu,J) + Cl- has been studied by means of the ab initio MO method and quasi-classical trajectory calculations. A strongly bound intermediate complex [FHCl](-) is found on the ground-state potential energy surface (PES) obtained by the ab initio MO method. The intermediate complex is most stable at the collinear form. By using a fitted ab initio PES, three-dimensional quasi-classical trajectory calculations are performed. The calculated rotational- and vibrational state distributions of the product HF(nu,J) are composed of two components. On the basis of the theoretical results, we propose a reaction model composed of two reaction channels : one is a direct channel in which products are in vibrationally excited states and in the rotationally ground state, and the other channel is a complex channel in which products are in rotationally excited states due to a long-lived [FHCl](-) complex. Rotational- and vibrational-state populations are reasonably explained by the two-channel model. In order to elucidate the selectivity of the reaction channels, the collision angle for each trajectory is analyzed. It is concluded from the trajectory calculations that collinear collisions lead to the direct channel, whereas both collisions at large impact parameters and side-attack collisions lead to the intermediate-complex channel.