The integration of sophisticated mesoscale air quality modelling systems, such as MM5-CMAQ and new generation of Computational Fluid Dynamics (CFD) modelling tools has been developed in this contribution. We have used an advanced and adapted version of the MIMO model (U. Karlsruhe, Germany) which is a sophisticated CFD model, to simulate the air concentrations at urban level with 10 m spatial resolution over the city of Las Palmas (Canary Islands, Spain). The CFD code receives the traffic emission data every second produced by a cellular automata model (CAMO). The integrated CFD model is called MICROSYS. This model is an Eulerian 3D tool which is running in diagnostic mode once every minute. The boundary conditions are obtained from the well-known MM5-CMAQ running over the city in prognostic mode. The MM5-CMAQ (OPANA V4) model is run with 1 km spatial resolution covering a domain of 16 × 16 km over the city. This system is operating in forecasting mode since 2004 and is operated over the Internet. The forecasting information for meteorology and air quality concentrations for the following 72 hours is used by MICROSYS to simulate the expected air concentrations at street level for the next three days. The system operates under daily basis and produces the detailed forecasting information at 6:00 GMT everyday. The Internet service includes a sophisticated VRML (Virtual Reality Modelling Language) tool to visualize in a 3D mode the air concentrations at street level by an Internet client. The VRML tool runs on the client server. We present also some comparative results related to the use of shared 64 bits memory machines and single 32 bits one-processor machines for CFD runs.