Like all forms of renewable energy micro hydroelectric power has recently attracted worldwide interest and yet the basic technology is not new. While seeming to offer power at extremely low annual running cost and with very few technical complications there are yet few countries where its use has become widespread. It is found that design installation and management have all to be treated very carefully. It has been demonstrated in many places that small hydro power can make a very important contribution towards rural development such as in the Peoples Republic of China where some 80000 mini hydro plants have been installed over the last twenty years. But there are pitfalls for the unwary. This paper introduces the techniques and a guide how to approach mini hydro projects. It is concerned only with systems of up to approximately 100kW output.