In this paper three evaluating parameters for cam lubrication characteristics in I.C. engine are introduced, namely the lubrication characteristic number Ns, the hydrodynamic characteristic number Nγ, and the non-dimensional lubrication characteristic number N̄s. The relations among them are deduced. From viewpoint of lubrication some basic points for the design of the cam profile are presented. The requirement for the condition Ns =0 is also proposed, i.e. (dNs /dϕ)Ns =0 ≥3mm/°. These evaluating parameters for cam lubrication characteristics of several current I.C. engines are computed, and finally some conclusions are drawn.