This article comprises the work of several research teams which analysed the effectiveness of solar water disinfection (SODIS) in various laboratory and field investigations carried out at different test sites over the last five years. SODIS was applied as batch and continuous flow process (SODIS reactor). The process is most effective with a water temperature of at least 50 °C. Transparent plastic bags allow a 3-log reduction (99.9%) of faecal coliforms and Vibrio cholerae through heating and radiation at an UV-A dose of 54 Wh/m² over a period of 140 min. The SODIS reactor produces around 100 L of drinking water per square metre of solar collector and day.