In addition to enhancing drilling safety and performance, MPD offers new options for well control. Because MPD allows rapid changes in bottom hole pressure, the response to an unwanted influx is not necessarily to shut-in and weight-up. Instead, the required overbalance can be regained dynamically without shutting in. The definition of dynamic well control varies across the industry. Most commonly, the term is applied to regaining overbalance conditions by closing an MPD choke while circulation is maintained. However, overbalance can also be obtained by increasing annular friction. The advent of dual gradient drilling offers further variation in dynamic well control practices. As MPD is a deviation from traditional drilling practices and the demonstration of the safety of dynamic well control is difficult, operational practices revert quickly to conventional shut in procedures despite the presence of MPD equipment. Inconsistent definitions and misunderstandings of dynamic well control amplify the problem of determining when dynamic well control is appropriate. The switch from dynamic MPD well control to conventional is controlled procedurally through the definition of operational decision points based on influx indicators and surface backpressure during drilling. The onus is on the operator to define these decision points such that dynamic well control is at least as safe as conventional techniques. In this presentation, a strict definition of dynamic well control is proposed. The work explores the key factors that must be considered in determining when the appropriate initial response to a well control situation is dynamic or conventional.