In an effort to expand its rural water supply and sanitation (RWSS) program in Thailand, A.I.D. contracted APHA to assess the impact of past A.I.D. RWSS projects in the country and to develop a strategy and options for further A.I.D. RWSS projects. Focusing their attention on the poorest of the rural poor, the APHA team, whose findings are here presented, visited 40 villages with an average population of 753 and representing 0.42% of 10 of the 20 provinces in which A.I.D. is participating in the Accelerated Primary Health Care (PHC) Project. Factors favoring implementation of an RWSS program in villages of less than 1,000 included the existence of the Ministry of Public Health (MPH) and its RWS/S Divisions, with their experience and their structure targeted to the local level; the success of past and present A.I.D./MPH programs, especially the ongoing PHC program; the existence of national RWSS targets; and the pressing need and desire of villagers for improved RWSS facilities. Constraints to an RWSS program are a lack of: trained personnel (including supervisory personnel) and transportation; adequate maintenance even for simple hand pumps; an adequate data base (including data on villagers' preferences regarding potable water sources); and a coordinated plan and funding. The following strategic actions were suggested: (1) assist in a detailed study of RWSS in all 20 provinces in the PHC program and develop an RWSS component for the project, arranging for four expatriates and 20 Peace Corps Volunteers to help develop and implement the component; (2) develop an MPH/USAID/T public health program and an RWSS project that can be implemented by MPH's RWS/S divisions; (3) provide training and transportation for MPH sanitationists; (4) train villagers in RWS/S; (5) help the RWS Division complete the proposed program's piped water supply portion and reestablish its maintenance responsibility; (7) train two RWS/S staffers, one each in the respective technical programs, and one each in management, supervision, organization, and logistics; and (8) develop options for water supply and excreta disposal interventions responsive to village needs (specific suggestions are included).