This paper examines the use of compulsory lincensing as a policy to combat the monopoly problem associated with the patent system. It introduces the notion of an optimal patent--one where the patent life and the licensing royalty rate are both determined optimally. Under certain simplifying assumptions it is shown that the optimal patent will have an indefinite life, for both process and product innovations. Some preliminary calculations suggest that the use of compulsory licensing may lead to substantial welfare improvements, even if the patent life is left unchanged at 17 years.