Summarizes attached French-language final evaluation (XD-ABI-186-A) of the urban upgrading sanitation program (4/85-12/93), part of a Housing Guaranty program in Tunisia. The program was implemented by the National Sewerage Agency (ONAS) in 30 urban slums and secondary towns. The sanitation program improved health and living conditions for some 118,000 persons in the targeted areas, even though targets for household sewer connections were not met, due to overestimation of the number of houses to be connected, and in some cases to technical difficulties or to householder refusal. Institutionally, the program's most important impact was the reorganization and decentralization of ONAS, which, however, increased its need for human and material resources. ONAS, which had to cope with numerous difficulties, gave proof of a remarkable capacity to adapt and displayed a good deal of technical know-how. Beneficiaries' reluctance to pay user fees has posed cost recovery problems and makes project replication difficult, in Tunis region, however, ONAS has succeeded in cost recovery by setting up a contract system which includes ONAS' costs in beneficiaries' water bills. Other problems included the absence of a training component, especially for regional teams responsible for project implementation; the overly complex nature of project-funded studies, which paid little attention to low-income residents' ability to afford sewage services; lack of a communication strategy to motivate residents to participate in project financing; delays due to various causes (rains, contractors, etc.); and problems in purchasing ground plots where purification stations were to be built.