Abstract: The model NMMB/BSC-CTM is a new fully on-line chemical weather prediction system under development at the Earth SciencesDepartment of the Barcelona Supercomputing Center in collaboration with several research institutions. The basis of the development is theNCEP new global/regional Nonhydrostatic Multiscale Model on the B grid (NMMB). Its unified nonhydrostatic dynamical core allowsregional and global simulations and forecasts. A mineral dust module has been coupled within the NMMB. The new system, NMMB/BSCDUST,simulates the atmospheric life cycle of the eroded desert dust. The main characteristics are its on-line coupling of the dust schemewith the meteorological driver, the wide range of applications from meso to global scales, and the dust shortwave and longwave radiativefeedbacks on meteorology. In order to complement such development, the BSC works also in the implementation of a fully on-line gas-phasechemical mechanism. Chemical species are advected and mixed at the corresponding time steps of the meteorological tracers using the samenumerical scheme of the NMMB. Advection is Eulerian, positive definite and monotone. The final objective of the work is to develop a fullychemical weather prediction system, namely NMMB/BSC-CTM, able to resolve gas-aerosol-meteorology interactions from global to localscales. Future efforts will be oriented to incorporate a multi-component aerosol module within the system with the aim to solve the life-cycleof relevant aerosols at global scale (dust, sea salt, sulfate, black carbon and organic carbon). In the present contribution we describe the statusof development of the system and first evaluation results of the gas-phase chemistry.