In this paper the utilization of Residue Number System (RNS) is investigated as a tool for variation-tolerant design. In particular circuits using various RNS bases are compared in terms of their sensitivity to the variation of process parameters. Furthermore, RNS advantages are quantitatively illustrated by considering a timing model. It is shown that for bases where all moduli channels are candidates to contain the critical path of the RNS circuit, the delay variation is reduced upto 86% when compared to the equivalent binary structures.