The Athens-Demokritos Urban background Monitoring station for Aerosol properties has been established at the campus of the National Centre for Scientific Research "Demokritos" since 2007. It lies in the ENRAACT field site away from direct emission sources in a suburban area in the North East corner of the Greater Athens Metropolitan Area and at an altitude of 270 m.a.s.l on the hillside of Hemetus mountain. The site is partly influenced by the Urban area and partly by incoming air from the North East and can be considred representative of the suburban atmospheric aerosol conditions. The Instrumentation and monitored aerosol and auxiliary parameters are listed below: Fine and Ultrafine Number Aerosol Size distribution (ambient and dry R.H.) Dry-Wet (90%) and thermally processed fractions (not continuous). Scattering Coefficient and Absorption Coefficient PM2.5. Fine and coarse mode number size distribution by Optical Particle counters. Mass concentration EC/OC (thermo-optical analysis). Aerosol Chemical Speciation (ToF) monitor for the Inorganic and Organic non-refractory species. Standard Meteorological data from a Mast at 10 m, Be7 aerosol monitoring initiated in 2011. Results are reported at the GAW-EBAS worldwide Database ebas.nilu.no