This report demonstrates, through data and analysis, how the airport environment can affect ATCRBS surveillance. The Lincoln Laboratory ATCRBS Monopulse Processing Subsystem was used to collect reply data at Memphis International Airport during March 1991. These data show a correlation between aircraft density, potential reflectors, and ATCRBS reply integrity. The number of replies has been shown to be directly related to multipath from reflecting surface, including taxiing aircraft. Additionally, it is shown that conditions can exist during which not all of the replies from ATCRBS equipped aircraft can be processed when forming target report measurements. Finally, it is shown that the bunching of replies in both time and space can introduce reply decoder overloading.