Rainwater Harvesting (RWH) is the process of collecting and storing rainwater for a later use. This technique could be an alternative water source in response of a climate change context. In this review, the state of this practice worldwide was studied. Some discrepancies between countries have been highlighted. First, between developed and developing countries, gaps concerning techniques and regarding the main purposes (water savings for the first ones and drinking purposes for the last ones) were reported. Then, within developed countries themselves, acceptance and standards of RWH installations are different, with precise guidelines and norms for countries leading the way on RWH practices. The scale of applications (RWH for households – up to 50 inhabitants, for large buildings and for urban area) is discussed and the state of the technique showed that there were more potential of technological development and challenges for large scale systems than for households. Finally, this report draws the attention to the needs in terms of Research and Development projects. Six main aspects were highlighted: drinking water, energy compensation, environmental impacts, economical aspects and the integration of stormwater management and rainwater harvesting. The last feature concerns hygienic aspect, but the report do not focus on this consideration.