SPECIATE is the U.S. Environmental Protection Agencys (EPA) repository of total organic compound (TOC) and particulate matter (PM) speciation profiles of air pollution sources. Among the many uses of speciation data, these source profiles are used to: (1) create speciated emissions inventories for regional haze, particulate matter with an aerodynamic diameter less than 2.5 micrometers (PM2.5), and ozone (O3) air quality modeling; (2) estimate hazardous and toxic air pollutant emissions from total PM and TOC primary emissions; (3) provide input to chemical mass balance (CMB) receptor models; and, (4) verify profiles derived from ambient measurements using multivariate receptor models (e.g., factor analysis and positive matrix factorization). This report documents how EPA developed the SPECIATE 4.0 database that replaces the prior version of the SPECIATE database (i.e., SPECIATE 3.2) that was posted to EPA's Clearinghouse for Inventories & Emissions Factors (CHIEF) web site in November 2002. SPECIATE 4.0 includes a total of 4,080 PM and TOC profiles (2,019 new profiles and 2,071 profiles carried forward from SPECIATE 3.2). SPECIATE 4.0 includes 1,361 new PM profiles (of which 95 are simplified profiles and 47 are composite profiles) and 648 TOC profiles (of which 11 are composite profiles).