A study of the application of reverse osmosis technology to the treatment of Hawaiian low quality waters was conducted. The purpose was to investigate the technical and economical feasibility of utilizing reverse osmosis technology to renovate waste waters after varying degrees of conventional treatment, and to desalt Hawaiian brackish groundwater from both basaltic and reef limestone aquifers. The experimental investigation of the technical feasibility of renovating waste water and desalting brackish groundwater was conducted with a small reverse osmosis pilot unit at four test sites on the island of Oahu. The operation of the reverse osmosis pilot unit in processing waste waters suffered from the problem of performance decline. However, the pilot unit's operation with brackish groundwater yielded promising results. Treatment expenditures of the two schemes were estimated at 97.8 and 103.2 cents per 1000 gallons of treated waste water. (Modified author abstract)