An analysis of morbidity was made in 11 kibbutzim (cooperative agricultural settlements), with a total population of 3,040, that had switched from nonwastewater to wastewater sprinkler irrigation or vice versa. Generally, partially treated stabilization pond effluent of poor microbial quality was used for irrigation. Vegetables or salad crops were not irrigated with effluent. The results showed that a seasonal, twofold, excess risk of 'enteric' disease was found in the 0 to 4 year-old age group during the summer irrigation months in those years in which wastewater was used for irrigation, compared with the parallel summer months of nonwastewater irrigation years in the same kibbutz. (Copyright (c) 1986 American Journal of Public Health.)