Doctoral thesis (PhD)Despite diarrhoea being the second leading cause of illness and deaths in children under five years of age globally, the relationship between settlement types (unplanned and planned) and caregivers' behavioural risk factors as well as the environmental risk factors for diarrhoea is not clearly known. The overall objective of this study was to determine the effect of type of household settlement on prevalence of childhood diarrhoea and associated risk factors in Mwanza City, Tanzania. A population based analytical cross sectional study, involving 480 children between 6 to 59 months of age was conducted from June to August, 2016. A structured questionnaire was used to determine the prevalence of diarrhoea in children, factors associated with childhood diarrhoea, association between settlement types and; prevalence of diarrhoea, caregivers’ behavioural risk factors, and the environmental risk factors for childhood diarrhoea. A binary logistic regression analysis was employed to test the risk factors for childhood diarrhoea. The overall reported prevalence of diarrhoea was about 20.4%. The regression analysis showed that the type of settlement did not have significant statistical association with neither caregivers‟ risk behaviour nor environmental risk factors for diarrhoea in children. Caregivers’ risk behaviours significant statistical associated with low risk of childhood diarrhoea included behaviour of washing hands; before preparing food, with soap and water after changing child’s napkins, of children with soap and water after toilet and before taking food. Environmental risk factors which include living in unplanned settlement, use of pit latrine and using faecal contaminated water were significantly statistically associated with higher prevalence of diarrhoea. It was recommended that health education programmes are needed in order to address identified behavioural and environmental risk factors. It was also recommended that further research should focus on determination of caregivers‟ knowledge on care of domestic water at household level in Mwanza City.