The monthly occurrence and mean age distribution of water-borne diseases in the Douala 4th District, Cameroon (1995–2006) were studied and probable causes of diseases spread were established. Diseases of interest included gastroenteritis, amoebic dysentery, typhoid fever and cholera. Water-borne disease occurrence was observed to follow a seasonal pattern with peaks occurring between the months of January and May followed by drops between June and October and rose again from November. Children below 5 years were found to be more vulnerable to diarrhoea, gastroenteritis, amoebic dysentery while persons between 15–44 years were more vulnerable to typhoid and cholera. Physico-chemically, water samples had turbidities varying between 5.5–86 NTU, pH values between 4.2 and 7.1 and zero residual chlorine. Bacteriological analysis showed that the total coliform count was averagely 74/100 ml, the faecal colform count was 43/100 ml and the faecal streptococci count was 27/100 ml. Lack of access to potable water, absence of sanitation facilities and environmental factors could be advanced as the probable causes of water-borne disease spread.