This paper is one of a series presented on behalf of the System Operations Subcommittee with the intent of focusing industry attention on current problems faced by electric utilities in the operation of the bulk power system. The paper is a compilation of short notes that describe the ramifications of loop flows on the power systems of the Penn- sylvania - New Jersey - Maryland Interconnec- tion, American Electric Power System, and the members of the Western Systems Coordinating Council. The operating problems caused by large loop flows are fairly well understood. The purpose of these short notes is to highlight the complexity of the problem and underscore the need for a full comprehension of the problem within the engineering community.