Locally testable codes (LTCs) of constant distance that allow the tester to make a linear number of queries have become the focus of attention recently, due to their elegant connections to hardness of approximation. In particular, the binary Reed-Muller code of block length N and distance d is known to be testable with O(Nd) queries, and has a dimension of N−(logN)logd. The polylogarithmically small co-dimension is the basis of constructions of small set expanders with many ``bad'' eigenvalues, and size-efficient PCPs based on a shorter version of the long code. The smallest possible co-dimension for a distance d code (without any testability requirement) is 2dlogN, achieved by BCH codes. This raises the natural question of understanding where in the spectrum between the two classical families, Reed-Muller and BCH, the optimal co-dimension of a distance d LTC lies --- in other words the ``price'' one has to pay for local testability.