This research, technique of the data mining used for help to find the characteristic of patient who used the insurance and the patient who unsed insurance for the data medic in Nganjuk Hospital. So that for the next can used for presume the step of the uses insurance in the future. Algorithm C4.5 can use for predict the step of use insurance with the pattern of the medic data before. In alogarithm C4.5 used for calculation entrophy and gain for get the node and another node. For this research the waterfall method used for software engineering method, in the processing of system were chronological and linear.