Introduction: User satisfaction is a key factor for the success of any information system. Evaluation of hospital information systems HIS is valueless without analyzing users' satisfaction. The purpose of this study was to survey the viewpoints of nurses, secretaries and paraclinic users about the usability of HIS in selected hospitals.

 Method: This cross-sectional study was conducted in 2009. A questionnaire, based on the international standard ISO 9241/10, was used to evaluate the usability of HIS. Initially, all hospitals in Tehran with HIS and companies providing the systems were identified. Then, a hospital from among the hospitals, supported by each company, was randomly selected. Finally, the usability of HIS was assessed from the perspective of nurses, department secretaries and paraclinic users through the standard questionnaire of IsoMetric. The collected data were analyzed by SPSS using descriptive statistics and one sample t-test.

 Results: The findings show that HIS usability was favorable from the perspective of nurses. However, it was perceived less desirable by paraclinic users.

Conclusion: The difference in viewpoints suggests that users' job affect the rate of their satisfaction. It is recommended that system providers pay special attention to the needs of paraclinic users, when designing HIS.