Artin approximation and other related approximation results are used in various areas. The traditional formulation of such results is restricted to filtrations by powers of ideals, {Ij}, and to Noetherian rings. In this paper we extend several approximation results both to rather general filtrations and to Cr-rings, for 2≤r≤∞.As an auxiliary step we establish the surjectivity of the completion map ▪ for a very broad class of filtrations.