We prove a conjecture of Il'yashenko, that for a C 1 map in R n which locally contracts k-dimensional volumes, the box dimension of any compact invariant set is less than k. This result was proved independently by Douady and Oesterl e and by Il'yashenko for Hausdorr dimension. An upper bound on the box dimension of an attractor is valuable because, unlike a bound on the Hausdorr dimension, it i...