The FOCUS_TOXSWA model calculates exposure concentrations of pesticides and their metabolites in watercourses and ponds, of the so-called FOCUS surface water scenarios. These concentrations are used in the pesticide registration procedure at EU level. The model concepts of TOXSWA are described briefly. The procedure for using the TOXSWA kernel (i.e. expert use) and related input files and output files are described. Concerning FOCUS_TOXSWA, the use of the graphical user interface to access the input and output is described. Input data are stored in a database. Pesticide entries resulting from drainage or runoff/erosion are accessed from separate files generated by FOCUS_MACRO and FOCUS_PRZM. Substance properties are accessed from the SPIN tool/database. Instructions for simulating a water-sediment study and a multi-year run are given.