The maximum blanket energy multiplication and the minimum thickness D-T fusion reactor blankets can be designed to have are estimated with the aid of the optimization code SWAN, using simplified blanket models. It is found that energy multiplications as high as 2 might be attainable. The minimum effective thickness of the breeding blanket identified is 7 cm or 8.5 cm, when C or PCA are used, respectively, for the reflector. All of these blankets use beryllium. Also performed is a preliminary partial feasibility study of a number of novel blanket concepts, including blankets using 6Li17Pb83, W, Zr and Cu as a primary constituent.