Dynamic underbalanced perforating1 is a technique for obtaining clean perforation tunnels resulting in much improved production or water injection. This technique has been successfully applied to several wells in the Ninian Field in the UK sector of the North Sea, resulting not only in better wells, but also in increased completion efficiency. In August 2003 a closed-chamber, dynamic underbalance shoot and pull operation was performed on Ninian North—a world first. The well came in at 50% higher production than expected. Since then, several other wells have been perforated using the same technique. Gauge data on the early wells showed the sequence of events, but did not capture the detail. A more recent well has been perforated using a new high-speed gauge that revealed the extent of dynamic underbalanced achieved. This paper describes the method, shows the results and discusses the value of using this technique.