The World Health Organization is developing guidance on water safety and health aspects of rainwater harvesting & storage. This will be a scientific contribution to the’ rolling’ revision of the WHO Guidelines for Drinking Water Quality. WHO acknowledges the need for a thorough assessment of the health aspects of collected rainwater, as increasing numbers of people and communities worldwide use rainwater for domestic purposes, including for drinking. This paper presents a review of microbiological and chemical issues, relevant to rainwater and health risks. Several concerns are raised that may need further consideration in design, maintenance and research in rainwater use.