The exponential growth of databanks in health care creates opportunities for knowledge generation using data mining. Advancements in information and communication technologies now mean that large quantities of data collected from different sources can be easily stored, secured and retrieved for analysis using databases. For data mining to be carried out the data sets from the different interacting source systems have to be organised in a data warehouse. Data mining offers the potential for exploring hidden patterns in data sets of a particular domain in this case health care. This can eventually be used to perform diagnosis and prognosis on different patient health care condition. Furthermore it places health care providers at a more informed point by enabling predictions hence through classification enhancing generation of new knowledge. This paper provides the state-of-art on data mining and its role on knowledge discovery in the health care sector.