Background
Diarrhea is known to be the major cause of mortality in children aged less than five years old. Although mortality from diarrheal disease is decreasing globally, morbidity is not. The objectives of this study were to determine the prevalence of diarrhea among under-fives and assess knowledge on causes of diarrhea among adults in Mkuranga district Tanzania.

Methods
Interviews with heads of households and observations were the methods of data collection employed by this study.

Results
The prevalence of diarrhea in children below the age of five years as reported by heads of households was 6.1% and most affected were children in age groups 12 – 17 and 18 – 23 months (11.6% and 15.8% respectively; p – value 0.001). The rate of diarrhea incidence was 1 episode per 10 children per week. The mean duration of diarrhea illness was 1.7 days. Most under-fives had diarrhea for one (38.1%) or two (24%) days. Respondents in the 4th least poor quintile were more likely to have comprehensive knowledge on causes of diarrhea compared to respondents in the 1st poorest quintile. Male respondents were two times more likely to have comprehensive knowledge than female respondents. Respondents with comprehensive knowledge on causes of diarrhea were less likely to have poor hand-washing practice and more likely to have received water, hygiene and sanitation education. Under-fives in age group 12 – 17 months and those from households with reported poor hand washing practice were more likely to experience diarrhea episodes.

Conclusion
Although prevalence of diarrhea reported in this study is low, the one week incidence is moderately high but less severe. Majority of household respondents had inadequate knowledge on causes of diarrhea and poor hand-washing practice. There is a need to provide WASH education to improve their knowledge on causes of diarrhea and hand washing practice.