In recent years, the industry has been pushing the application window for inflow control technology, e.g. inflow control devices (ICDs), to harsher environments, including low-permeability formation rock, high-rate stimulation, and stricter inflow conformance for improved reservoir management. These trends result in significantly increased pressure drops and flow velocities across the equipment leading to an increased failure risk due to mechanical limitations and higher erosion/corrosion potential, as recently observed in a Middle East application. To understand long-term reliability of the equipment, accurate predictions of ICD performance are crucial. This paper presents the initial part of a comprehensive program to characterize the performance and operational envelope of commonly available ICDs. The focus of the current work is on two-phase (immiscible liquid) flow performance testing using water and three oil viscosities (2–60 cP at a test temperature of 200 °F) and on single-phase gas testing using nitrogen. As a test sample, a 6-5/8 inch liner is used with perforation diameters similar to commonly available ICD nozzle sizes. For the two-phase flow testing, data for five different water cuts and five pressure drops for all three viscosities will be presented, while for the single-phase gas testing, performance correlations for several upstream pressures and five different ratios of upstream to downstream pressure will be discussed. The detailed experimental setup and the testing methods will be outlined in order to highlight the necessary factors that need to be considered to approximate downhole flow behavior in a laboratory environment. Moreover, the results will help to establish standardized testing procedures for inflow control devices in order to provide operators reliable data mandatory for ICD completion design, long-term well performance and completion lifetime predictions.