The application of data mining methods and tools that can help to explore large quantitiesrnof data generated by the Call Detail Record (CDR) of telecommunication switch machinernwill be the art of the day to address the serious problems of telecommunication operators,rnThe CDR consists of a vast volume of data set about each call made and it is a majorrnresource of data for research works to find out hidden patterns of calls made byrncustomers in addition to the typical use for bill processing activities,rnMore importantly, data mining techno logy has enabled telecommunication companies tornutilize this generic source of data for different kinds of customer relation shiprnmanagement and marketing activities including fraud detection and prevention StrategiesrnThe methodology used for this research had three basis steps these were collection ofrndata, data preparation and model building and testing, The required data set was selectedrnand extracted from the billing data set of Ethio- mobile, Neural network data miningrntechnology were employed to build and test the model s, The c1ata mining mcthod used inrnthis research work have proved to yield comparably suJ'fi cient results for practical u s~ asrnfar as supportive mechanisms are employed fo r the misclass ification of fraudulentrncustomers as non-fraudulent and vice versa, Due to this fa ct the telecornmunicationrnoperators should take serious and intensive follow ups for unusually high frequency andrnlong duration of international calls made by some possibly fraudulent customers customersrnHowever these lection of representative sample data for the whle database of thernproblem under consideration needs a series consideration and care to proply sdcct therntraining data set. Otherwise due to the rare occurrences of possibly fraudulent calk therntraining of representation data set will be a tedious activityrnIn this research work, the researcher has proved that the CDR is a major resource of orrncrucial knowledge about customers of Telecomm citation Corporation, Beside that thernnumber of calls made and the duration of each call should be traced to proper Know rnunhealthy customers of the corporation, Finally it is a rich field for research for other rninterested researchers to make further and in-depth research to this area ,