The Mexican border areas of Texas possess many unique characteristics that are not present in other parts of the state. One of the most obvious is the prevalence of Spanish as the primary language. Another characteristic is the large number of drivers from Mexico. These two factors may limit the ability of border area drivers to understand traffic control devices. The research study was conducted to determine how well drivers from Mexico understand 33 of the more significant traffic control devices used in the United States and Texas. The survey utilized flash-cards with open-ended questions to assess comprehension levels. It was administered to northbound traffic with Mexican license plates at international bridges in two Texas border cities. Driver responses were recorded on audiotape and later separated into several categories, including correct and partially correct. The analysis of the responses indicate that, of the 45 questions that were asked about the 33 traffic control devices, approximately half (23) had correct and partially correct response rates of over 80 percent. Approximately a third (15) had correct response rates of over 80 percent. Many of the devices with lower comprehension levels among Mexican drivers are the same devices that have lower comprehension levels among Texas drivers.