Two decades of discussion has still to clear the fog surrounding the validity of the PLC concept. This paper reviews available evidence, and attempts to identify some of the issues that PLC researchers need to address. Literature pertaining to the following dimensions of the PLC concept have been examined: a) Empirical investigations b) Theoretical investigations c) Managerial applications of the PLC concept d) PLC in international trade. Finally, PLC has been evaluated as a theory. The conclusion is that the PLC concept falls substantially short of fulfilling the requirements of a theory. This will be possible only if hypotheses for PLC patters that are product-specific, market-specific, and time-specific, can be proposed and tested. These will have to include provisions for variations in PLCs, in response to changes in exogenous variables.