Background: Short-STEM prosthesis for total hip arthroplasty (THA) have been designed to overcome the weakness of standard-STEM prostheses and improve surgical outcomes. The aim of this study was to compare short-STEM with standard-STEM prosthesis outcomes.Methods: This study was performed as a randomized clinical trial. Subjects were selected among patients referred to Sina University Hospital, Tehran, Iran from April 2010 to 2012. THA were performed with short-STEM or standard-STEM prostheses after obtaining written informed consent from patients. Balanced block randomization method was used to get a random sample in each group. Clinical outcomes were evaluated based on Harris Hip Score (HHS). Patients were followed up for at least one year. All patients were examined at 2 weeks, 6 weeks, 3 months, 6 months and one year after surgery. In each visit, Control X-ray was obtained and bone and prosthetic position were assessed. Also, the symptoms such as infection, pain, claudication, ability to climb stairs, using crutches and weight bearing were rechecked. Student t-test was used to compare outcomes in the two groups.Results: A total of eighty four THA were studied. 13 patients were lost to follow-up or had infection and failure. One patient died with the prosthesis in situ from causes not related to the surgery. Therefore, a total of 70 patients were analyzed. Of these, 34 and 36 hips underwent small STEM and standard STEM THA, respectively. The mean age of the patients at the time of operation was 61.1±8.68 years (range, 48-86 years). Most common reasons for arthroplasty were osteoarthritis, avascular necrosis and dysplasia of hip. There were significant differences between the two study groups in bleeding during surgery (P=0.001). There were no significant differences among the study groups in HHS except for 6th week and 3th month (P=0.000).Conclusion: The use of short-STEM prosthesis can improve the performance of patients in short-term but no significant difference with standard-STEM prosthesis in long- term.