Data on the number of admissions for diarrhoea each week to the West Kalimantan Provincial Hospital, Pontianak, Indonesia over a 5 year period, 1992-1996, were collected. After cleaning and exclusion of extreme values, transformation was then performed to ensure that the data were free of special cause variation and normally distributed. A control chart was then constructed to provide an 'early warning' system for hospital authorities in order to facilitate the management of the epidemic and to improve patient care.