Abstract By-passed pay can occur at or between wells. Either way, it constitutes a lower risk prospect than hydrocarbon accumulations in unappraised areas. Beyond this, there are three contemporary drivers for its exploitation. First, new technology in the form of sharper reservoir imaging allows insights that were not achievable previously. Second, an evolving understanding of how reservoirs work has led to improved procedures for maximizing the exploitation of even the most problematic accumulations. Third, market forces amid global post-peak production fears are giving the incremental development of by-passed pay an even greater commercial impetus today. An examination of case histories that illustrate the role of these drivers has led to a six-fold type classification of by-passed pay. Type 1 can be produced using an existing identified well. Type 2 requires a side track or a new well in order to capture the reserves. Each type is further subdivided into three classes. The classification scheme has provided the context for an emerging modus operandi to maximize commercially recoverable hydrocarbons in developed assets. Thus, the approach takes the form of a road map for practical application. By corollary, the type classification demonstrably accommodates a wide range of reported exploitations of by-passed pay from diverse reservoirs. Therefore, this classification constitutes a potential foundation for further systemic refinements to the identification and recovery of by-passed pay.