Faced with cost, time, or other pressures to keep an experiment small, blocking can be an effective tool for increasing precision of treatment comparisons. The simplest implementation of blocking is a division of experimental units into two equi-sized subsets, allocating one degree of freedom to explain unit heterogeneity. Small experiments will have block size k smaller than the number of treatments ν being compared. This paper solves the problem of optimal allocation of treatments to two small, equi-sized blocks. The solution depends on the optimality criterion employed as well as the ratio k/ν.