Cross border situations complicate epidemiologic risk assessments in transboundary regions such as the US-Mexico border. Countries have different health policies, mosquito control policies, and mosquito surveillance systems. We established a binational Aedes mosquito surveillance program in Reynosa, Tamaulipas, and McAllen, Texas by replicating a part of the Mexican Integrated Vector Monitoring System (IVMS) across the international border. The entomologic surveillance of the IVMSs is based on ova collection cups (ovitraps) and for the binational project, the surveillance protocol was modified to include an Autocidal Gravid Ovitrap (AGO) in the center of every city-block (100 m2) distribution of four ovitraps. We measured the weekly abun-dance of Aedes eggs and adult females in 72 clusters (cluster = one AGO and four ovitraps) in Reynosa and 67 clusters in McAllen from Epidemiologic Week (EW) 17 to EW 36. The mean weekly egg counts were 34 and 22 in McAllen and Reynosa respectively. The female adult mosquito counts were more than 5 in 12 out of 20 (60%) weeks in McAllen, and in 5 out of 16 (31%) weeks in Reynosa. For every increase of one female mosquito, the egg counts in the corresponding ovitraps increased by 2.33% (95% HDI: 2.31%–-2.42%) in McAllen and by 0.6% (95% HDI: 0.5%–0.62%) in Reynosa. Counter knowledge, weekly increase of temperature had a negative influence in adult and egg counts in Reynosa and McAllen. Precipitation had a positive influence on egg counts in McAllen
