Abstract: A specially designed desalinization unit utilizing solar energy has been tested under actual weather conditions. Chief factors that influence the freshwater yield have been investigated. Suitable ranges of factors were confirmed. As a result of the adoption of multi effect thermal regeneration and other measures to improve the thermal performance of the system, yield of the system was enhanced to about 2 5 times greater than that of a conventional single basin type solar still under the same conditions of thermal energy input.