Expressions for Coulomb collision rates in the magnetised plasma physics and nuclear fusion literature are reviewed. General collisional momentum and energy exchange rates are given for plasma particle species assumed to be in local thermodynamical equilibrium. Specific expressions for a simple plasma are then compared with those presented in numerous standard references. Differences by factors of order unity are found in several sources and are linked to the replacement of the reduced mass by the test particle mass at some stage of the derivation.