The magnitude, and the superficial and temporal distribution of non-methane volatile organic compounds (NMVOC) emitted by vegetation in Catalonia for the year 2000 have been estimated, as a first step to using a chemical transport model (CTM). Vegetation represents an important source of isoprene, monoterpenes and other volatile organic compounds (OVOC) whose interactions and reactions in lower troposphere are important constituents involved in photochemical pollution episodes. This estimation was developed using a high-resolution land-use map (squared cells of 1 km2) that differentiates twenty-two categories. Air temperature and solar radiation for the year 2000 were collected from different meteorological surface stations. We have used a standard biogenic emissions mathematical model built into a geographic information system (GIS) software. In comparison with other estimations made before, this uses new information, mainly related to some recent emission factors for typical Mediterranean species; and better knowledge of the composition of Catalonia's forest cover; implying therefore a qualitative uncertainty improvement. Results indicate an annual cycle with increasing values in March - April and the highest emissions in July - August followed by a decrease in October - November. Annual biogenic NMVOC emission reaches 55.7 kt, being monoterpenes the most abundant (29.2 kt), followed by OVOC (16.0 kt) and isoprene (10.2 kt), which represent 53, 29 and 18 percent of total emissions, respectively.