The goal of the MACC (Monitoring Atmospheric Composition and Climate) project is to operate and improve data-analysis and modelling systems for a range of atmospheric constituents that are important for climate, air quality and surface solar radiation. Product lines include data records on atmospheric composition for recent years, data for monitoring present conditions and forecasts of the distribution of key constituents for a few days ahead. MACC is funded by the European Union and provides the pre-operational atmospheric environmental service of the European Global Monitoring for Environment and Security (GMES). This service complements the weather analysis and forecasting services provided by European and national organisations by addressing the composition of the atmosphere. We will describe the different components of the project, the products currently delivered or planned within MACC, and how the scientific community can have access to the MACC products.