Abstract. Metric dimension is the minimum size of a subset of vertices which distinguish all pairs of vertices by means of distance. We prove that for t>=5 the metric dimension of circulant graph Cn(1,2,...,t) is at least \lceil 2t/3\rceil +1 with equality if and only if t=5 and n=13. Hence dim(Cn(1,2,...,t)) \ge \lceil 2t/3 \rceil + 2 for t\ge 6 and this bound is sharp for every t\ge 6.