We investigate the maximum size of a Subset of the edges of the n-cube that does not contain a square, or 4-cycle. The size of Such a subset is trivially at most 3/4 of the total number of edges, but the proportion was conjectured by Erdos to be asymptotically 1/2. Following a Computer investigation of the 4-cube and the 5-cube, we improve the known upper bound from 0.62284 ... to 0.62256 ... in the limit. (C) 2008 Elsevier B.V. All rights reserved.