The problem of drawing maximum power from an

port by suitably terminating it with another passive

port is studied. Methods are derived for determining sets of passive impedance matrices which are "optimal" in the sense that they draw maximum power from a given

port. It is shown that, in all nontrivial cases, if there exists any (passive or otherwise) optimum-load impedance matrix, then there exist, in fact, infinitely many passive optimum-load impedance matrices.