Israel experienced a large number of waterborne disease outbreaks between 1975 and 1985, followed by a steep decline in the period 1986-92. Large-scale community waterborne disease outbreaks occurred primarily in the late 1970s, and in 1985 (the Krayot, four small towns neighboring Haifa), but substantial outbreaks occurred as late as 1989, with 4 during 1986-90, and 1 during 1991-92. New water standards, including mandatory chlorination of all community water supplies, came into effect in late 1988. Water quality, as monitored by the Ministry of Health, showed a marked improvement even when measured by the more stringent standards of the 1988 regulations. Long-term trends in the total of reported enteric infectious diseases from all sources, including typhoid, hepatitis, Shigella and Salmonella in Israel are examined. Typhoid, which has been declining since the 1960s, peaked in 1985 with the large waterborne disease episode of the Krayot. Shigella and total hepatitis incidence increased slowly up to the mid-1970s, followed by large increases during the 1975-85 period, then by a rapid decline up to 1991. Shigella, from childhood contacts in kindergartens, increased in 1992. Salmonella incidence continues to increase steadily. Mandatory chlorination and more stringent water standards have had an important impact on water quality and on waterborne disease outbreaks in Israel. Empiric evidence suggests that improving water quality may also be a factor in the changing patterns of some enteric diseases and the total burden of enteric disease in Israel.