The purpose of this analysis was to examine pilot-controller communication practices in the TRACON (Terminal Radar Approach Control) environment. Forty-eight hours of communications recorded on the voice tapes from eight TRACONs were analyzed. There were 13,089 controller-to-pilot transmissions examined in this study. This included 9,409 clearances (e.g., assignment of attitude; instructions to change heading, speed, or radio frequencies; instructions for arrival, etc.) and 3,680 requests for information, salutations, etc. The complexity of the controller's message (i.e., the number of pieces of information) was examined and the number of erroneous readbacks were analyzed as a function of message complexity. Pilot acknowledgments were also analyzed; the numbers of full and partial readbacks, and acknowledgments only (i.e., 'roger') were tallied. Pilot reports of altitude information was also examined. Fewer than one percent of the messages resulted in communications errors. Among the error factors examined were: complexity of the message, type of acknowledgment, use of call sign in the acknowledgment, type of information in error, and whether or not the controller responded to the readback error. Instances in which the controller contacted the aircraft with one call sign and the pilot acknowledged the transmission with another call sign were also examined. The report concludes with recommendations to further reduce the probability of communication errors.