An anomalous high-altitude voltage breakdown on a VHF antenna aboard Nike-Cajun Rocket AD 6.841 is investigated. A previously proposed cause of the anomaly, a dynamic pressure variation interacting with a multipactor discharge, is experimentally investigated. The multipactor discharge under dynamic pressure conditions results in a unique form of voltage breakdown hitherto undescribed. This discharge form is called a gas-augmented-multipactor GAM discharge. The GAM DISCHARGE MAY PERSIST FOR SEVERAL MINUTES Certain aspects of the GAM discharge more closely resemble the usual gas discharge breakdown than they do the usual multipactor discharge. The GAM discharge has an effect upon antennas comparable to that of the usual gas discharge breakdown at certain pressures in the latters operating regime. The flight-test record is examined and compared with the laboratory data. It is concluded that the anomalous breakdown was due to a GAM discharge.