A multiphase flowmeter was used in addition to conventional surface well-test equipment during five deep offshore exploration drillstem tests. Several immediate benefits were derived. The cleanup phase was monitored, which improved control of the formation drawdown as well as the prediction of well eruption. The flow history was better quantified, which improved the pressure-transient analysis. The instantaneous flow-rate measurements shortened flow periods and accelerated the decision process, reducing the overall test duration. In general, the multiphase flowmeter enhanced operation flexibility, confidence in the information acquired, and accuracy of the results.