Due to the increasingly documented prevalence of diarrhoeal diseases in Malaysia, a number of water-related programmes have been implemented in an attempt to improve health status through the reduction of incidence of waterborne communicable diseases associated with poor public water supplies. The implicit assumption underlying these projects is that the enhancement of the physical infrastructure, and subsequent improvements in the quality of the water supply, will substantially reduce waterrelated disease. This thesis questions the veracity of this hypothesis, and therefore the justifiability of an emphasis upon engineering and urban infrastructural interventions. Research centred upon Port Dickson, a district which typifies existing water and sanitation conditions in much of semi-rural Malaysia. The specific objectives of the thesis were: to determine the measured burden of illness of waterborne disease within the district and to estimate levels of underreporting; to determine morbidity-related factors influencing the decision to seek medical treatment; to provide a demographic profile of the population experiencing diarrhoeal episodes; and to identify risk markers or predictors of morbidity. Burden of illness was measured by health services utilization, while values for underreporting and risk markers were derived from a 268 household diarrhoeal morbidity survey. Diarrhoeal incidence was estimated to be 12-16% annually, much higher than Malaysia's official average. This incorporated a rate of non-reporting of 19~, which was influenced by chronicity, duration and severity of episodes. Individuals found to be most at risk were young children and adults in their child-bearing years, minority racial groups, and those with poor water supply and sanitation infrastructure and inappropriate hygiene habits. While water quality was found to influence diarrhoeal rates, factors in addition to infrastructure - partially hygiene - were shown to play a greater role. Thus, it is suggested that the impact of water and sanitation improvement projects would likely be minimal, unless accompanied by complementary behavioural education programmes. The spatial bias of the aforementioned risk factors suggests a need to refocus intervention initiatives upon rural areas. / Thesis / Master of Arts (MA)