The Los Angeles Basin ADS-B Measurement Trials provided a quantitative assessment of the existing interference environment at 1090 MHz and the surveillance performance of Mode S Extended Squitter in that environment. Redundancy in the measurement equipment and in the flight configurations chosen during the trials provided extensive cross checking capability, and greatly increased the integrity of the results. ATCRBS reply rates as high as 40,000/second above -90 dBm were measured. The corresponding aircraft distribution and 1030 MHz interrogation rates correlated well with these measurements. A wide range of scenarios were captured to measure the airborne and ground-based reception of ADS-B Extended Squitters emitted by airborne sources. Air-to-air ranges of greater than 100 nmi were routinely observed, and comparison with ADS-B MASPS requirements showed that all airborne requirements were met in the scenarios flown. Air-to-ground reception rates were routinely better than the update rates provided by either en route or terminal radars at ranges beyond 150 nmi. Ground-to-air (uplink) performance was adequate to support transmission of ADS-B or other information in broadcast formats within approximately 60 nmi of the ground station. Finally, these measurements are a valuable source of validation and refinement data for the various models used to predict Extended Squitter performance in current and future scenarios.