As part of an initiative to encourage the uptake and understanding of wastewater treatment process modelling, WRc (UK) is to make its dynamic wastewater treatment modelling programme, STOAT, available as Freeware. STOAT has been widely used for modelling wastewater, industrial effluent and biosolids treatment processes throughout the world by utilities, consultants and universities. In the past few years, modelling of wastewater treatment processes for design and optimisation has gained general acceptance in the water industry. However, commercial software packages still represent a significant financial investment which is precluding its universal uptake. WRc hopes, by making its commercial software package available as freeware through its own website, to encourage more use of dynamic modelling in design and optimisation leading to a better understanding of the fundamentals of wastewater treatment processes as a science.