The ASAD software package frees the atmospheric chemist from writing code to solve chemical time dependent equationsand can be used for a wide range of problems including stratospheric chemistry, tropospheric chemistry or pollution studies, and for 1D, 2D and 3D models. Since little programming is required, the effects of programming errors are greatly reduced and consistent results between different models ensured. Through the use of input files to list the desired chemical species and their properties and the chemical reactions, different chemical scenarios can be rapidly developed and tested without any additional programming.ASAD comprises a plug-in subroutine library to solve atmospheric chemistry time-dependent problems, a chemical reaction database and utility programs. ASAD has been designed to be coupled to any type of atmospheric model and be used as far as possible as a ‘black box’. The code has been carefully optimized for performance and it will vectorize well on machines with this capability. It includes a choice of integrators based on published methods and supports approximations often used in atmospheric chemistry modelling, such as chemical families, fractional products and the steady state approximation. ASAD also supports the inclusion of user-supplied schemes for wet and dry deposition, source emissions, heterogeneous chemistry and photolysis.