en Aims: Evaluation of Patient Satisfaction (PS) is one of the most essential factors in improving the quality of healthcare systems. The aim of this study is to determine the norms and to evaluate the validity and reliability of the Najmiyeh Outpatients Satisfaction Questionnaire (NOSQ). Methods and Materials: This study has been conducted on 240 outpatients in Najmiyeh subspecialty hospital (Tehran-Iran) in 2011. They were selected using the proportional simple random sampling method. Following the confirmation of the content validity, we considered the construct validity and reliability applying Confirmatory Factor Analysis (CFA) and Explanatory Factor Analysis (EFA) and Cronbach's Alpha. Also, SPSS and AMOS version 18 were used for data analysis. Findings: The sample population consisted of 240 subjects, including 132 females (55.1%) and 108 males (44.9%). The EFA reported three important factors in this regard, with a variance of 54% and Kaiser-Meyer-Olkin index of 0.82, all approved by the CFA (RMSEA= 0.04, CFI= 0.96). The outpatients' satisfaction factors were: “hospital information system, treatment and conditions”. The reliability of the questionnaire was reported at %71 based on the Cronbach's alpha. Conclusions: Both validity and the reliability indexes of the NOSQ have been reported at a desirable level; therefore it can be used as a valid and reliable instrument to measure the outpatients' satisfaction. Standardization,Outpatients' satisfaction,Reliability,Validity 13 20 http://hehp.modares.ac.ir/browse.php?a_code=A-5-1000-7609&slc_lang=en&sid=4 Mohammad Gholami Fesharaki Mohammad Gholami Fesharaki 100319475328460040345 100319475328460040345 Yes Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Mohammad Javad Jamali Mohammad Javad Jamali 100319475328460040402 100319475328460040402 No Baqiyatallah University of Medical Sciences, Najmie Subspecialty Hospital, Tehran, Iran Baqiyatallah University of Medical Sciences, Najmie Subspecialty Hospital, Tehran, Iran Fatemeh Rahmati Najarkolaei Fatemeh Rahmati Najarkolaei 100319475328460040403 100319475328460040403 No Health Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Health Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Masome Mohamadian Masome Mohamadian 100319475328460040404 100319475328460040404 No Baqiyatallah University of Medical Sciences , Najmie Subspecialty Hospital, Tehran, Iran Baqiyatallah University of Medical Sciences , Najmie Subspecialty Hospital, Tehran, Iran Mehdi habibi Mehdi habibi 100319475328460040405 100319475328460040405 No Iran Helal Institute of Applied Science & Technology, Tehran, Iran Iran Helal Institute of Applied Science & Technology, Tehran, Iran Zohreh Aghamiri Zohreh Aghamiri 100319475328460040406 100319475328460040406 No Baqiyatallah University of Medical Sciences, Najmie Subspecialty Hospital, Tehran, Iran Baqiyatallah University of Medical Sciences, Najmie Subspecialty Hospital, Tehran, Iran