As part of the EPA's ongoing in-use vehicle emissions compliance program, two hybrid vehicles were tested. A 2001 Honda Insight and a 2001 Toyota Prius were tested on a chassis dynamometer at the National Vehicle Fuel and Emissions Laboratory. Both vehicles were run on the Federal Test Procedure drive cycle. Emissions were measured simultaneously using the SEMTECH-G Portable Emissions Measurement System (PEMS) for comparison to the chassis dynamometer bench analyzer. The correlation for cumulative emissions (bag) between dynamometer and on-board analyzer were adequate for CO2, CO, and NOx, though the PEMS HC measurements were low by comparison. The measurements were limited by the very low exhaust volume flow rates on both vehicles. A more sensitive flow meter will be required to measure emissions from vehicles certified to SULEV standards. A more detailed analysis of the second-by-second data indicates that during the driving modes where most of the emissions are occurring (cold start, catalyst breakthrough), both analyzers adequately captured emissions. With improvements to the flow meters, the modal measurements from the PEMS should be more useful for modeling purposes, however further study will be required.