The purpose of this research was to analyze the risk factors of diarrheal disease in children age 0-5 years and to construct an equation for forcasting probability to get diarrhea from these factors. The samples randomly selected by 2-stage probability sampling were 466 children in Singhaburi Province. The data were collected from two sources

the records from the health officials in villages and the persons who looked after their children. The results revealed that the incidence rate of diarrhea by survey in July, 1989 was 14.59%, higher than the rate of the official recods (5.36%) from the health centers. Using the technique of stepwise logistic regression, the risk factors of 4 age groups of children (under 1 year, 1-2 years, 2-3 years, and 3-4 years) when using the group of 4-5 years of age as the based group, showed the relative risks of 24.0, 16.1, 9.5 and 7.3 respectively. The nutritional status of children classified by weight for age indicated two malnutrition group, 1st and nd -3rd degrees. When using the normal children as the based group the first group had the relative risk of 3.6 where as the second group had the relative risk of 6.1. The other important factors ranked by the values of relative risks wer knowledge and health believes about diarrhea in children of person who looked after their children (88.3, 45.2), incorrect health behavior (6.0), childrens illness (5.9), low income (2.8) and the person who looked after their children but not childrens father-mother (2.7). The equation for forcasting probability to get diarrhea (P1) was P1 = 1/(1 + exp(-{-6.56 + 3.18 (under 1 year) + 2.78 (1-2 year) + 2.26 (2-3 years) + 1.98 (3-4 years) + 1.05 (income < 500 baht/capita/month) + 1.79 (mothers bad health behavior) + 3.81 (mothers wrong health believe) + 1.77 (history of childrens illness eg, URI. or hypersensitivity) + 1.27 (1st degree of malnutrition W/A) + 1.81 (2nd -3rd degree of maluntrition W/A) + 0.99 (person who look after children but not father-mother) + 4.48 (lacking of knowledge about diarrhea) + 0.46 (fair level of knowledge about diarrhea).