We consider the surface plasmon resonance established along an interface between a metal and a chiral medium (chiral case). Resulting solutions are compared with those obtained for a metal-dielectric interface (achiral case). We found that the chiral case exhibits either larger or smaller phase speeds than the achiral case due to the energy redistribution between translation and rotation. For a loss-free system, we found crossovers among the dispersion curves and spatial inversions in field profiles. These features are associated with anti-symmetric spin flips with respect to medium chirality. The short-wavelength limit leads to an upper bound on the medium chirality.