The emergence of Venezuelan equine encephalitis virus in Chiapas Mexico was examined from a field approach and from a laboratory approach. This virus was not previously associated with equine disease in Mexico. The evolution of the equine virulent phenotype was thought to have resulted in a mosquito vector switch from Culex (Melanoconion) taeniopus to Aedes (Ochlerotatus) taeniorhynchus as a result of land-use changes. Wild rodents and mosquitoes were captured over the course of one year and little evidence of virus circulation was found. Wild rodents from five species were then imported into the lab for experimental evaluation as virus amplifying hosts. It was found that a VEEV strain from the study area may use a variety of rodents as amplifying hosts in the laboratory. Lastly a breeding colony of Culex (Mel.) taeniopus mosquitoes was established and experimentally evaluated for the ability of these mosquitoes to transmit equine virulent VEEV. It was found that equine virulent virus infects and is transmitted by this mosquito with high efficiency and is likely maintained in transmission foci by Culex (Mel) taeniopus during inter-epizootic periods. These findings emphasize the importance of continual surveillance and equine vaccination.