The use of irrational drugs is a global issue that can decrease public health. Some examples of using drugs irrationally are polypharmacy, the use of nonessential drugs, the use of inappropiate antimicrobial, the excessive use of injection, the prescription writing is not accordance with clinical guidelines, the patient are disobdient and they treat themselves improperly. The objective of this research is to know the rationale of drug use associated with prescribing patterns in patients in outpatient facilities PKU Muhammadiyah Gamping Hospital period January - June 2017 based on WHO 1993 indicator. This research is non-experimental descriptive research. The data were taken retrospective from the prescription of outpatient at PKU Muhammadiyah Gamping hospital. Then, the data were analyzed based on WHO Indicator 1993. The samples of this study were 600 prescription. They were chosen by using systematic random sampling method. The research showed that the average number of drugs per prescription was 2,12 item, it was suitable with indicators WHO 1993 was 1,8-2,2 item. The percentage of prescribed generic drugs was 61.83% lower than WHO 1993 standard of> 82%. The percentage of antibiotic prescribing was 20.5% according to 1993 WHO standard <22,7%. The percentage of drug prescribing with injection stocks was 3.83% higher than the WHO 1993 standard of 0% and the percentage of prescribing medications corresponding to the Hospital Formula was 98.54% lower than WHO 1993 standard of 100%. The conclusions obtained in the research is PKU Muhammadiyah Gamping Hospital Related Pattern of Prescribing In Patients In Outpatient Installation Period January - June 2017 Based on WHO Indicator 1993 has done the best for prescribing pattern given to the patient.