The patient classification system is to assess patients group them with patients having similar needs and assign patients in each group a numerical score to quantify their nursing care needs for staffing. The purpose of this study is to develop a predictive and metodologic , validity and reability patient classification instrument desined for medical and surgical wards. The study is conducted in the hospital which is a 222 bed, surgical and medical wards and the nurses (90 nurses) who worked in this wards. The study is designed for three steps in February 2002- January 2003. The patient classification system was discussed in the first step. A study team was constituted for develeop a patient classification instrument and fourteen meeting was created in the second step. During the third step establishing a validity and reability patient classification instrument. At the end of the third step, Kendall 's coenfficient of concordance is 0,90 (P<0,000) and Pearson's correlation coenfficient is 0,87 (P<0,000) and item- total correlation is 0,93 and Crombach's Alfa mterrater reability is 0,82 of the patient classification instrument was found . The classification instrument consist of 32 patient care needs criteria and 7 basic area and classifiy the patient 5 categorizes.