Measurements were conducted to characterize the sources and processes of primary and secondary particulate matter (PM) and precursor gases in the California-Mexico Border Region (Cal-Mex) in 2010, in a collaborative research project between the Molina Center for Energy and the Environment, Scripps Institution of Oceanography/University of California at San Diego, Texas A & M University and Virginia Tech. The objective of the Cal-Mex campaign was to characterize the transport, transformation, and impacts of gaseous and PM pollutants on regional air quality and climate change. The instruments from the Texas A&M team included Proton Transfer Reaction Mass Spectrometer (PTR-MS) for a suite of VOCs, Ion-drift chemical ionization mass spectrometry (ID-CIMS) for H2SO4 vapor, Tandem-differential mobility analyzer (TDMA) and DMA-aerosol particle mass analyzer (APM), Cavity ring-down spectrometer (CRDS) and nephelometer for extinction and scattering coefficients of soot aerosols. In this talk, we will present measurements of aerosols (size distribution, effective density, volatility, hygroscopicity, optical properties) and gaseous species (VOCs, sulfuric acid) measured at the California-Mexico Border.