In the health informatics field, usability studies typically focus on evaluating a single information system and involve a rather small group of end-users. However, little is known about the usability of clinical information and communication technology (ICT) environment in which healthcare professionals work daily. This paper aims at contributing to usability research and user-oriented development of healthcare technologies with three objectives: inform researchers and practitioners about the current state of usability of clinical ICT systems, increase the understanding of usability aspects specific for clinical context, and encourage a more holistic approach on studying usability issues in health informatics field. A national web questionnaire study was conducted in Finland in spring 2010 with 3929 physicians actively working in patient care. For the purposes of the study, we described three dimensions of clinical ICT system usability that reflect the physicians' viewpoint on system usage: (1) compatibility between clinical ICT systems and physicians' tasks, (2) ICT support for information exchange, communication and collaboration in clinical work, and (3) interoperability and reliability. The dimensions derive from the definitions of usability and clinical context of use analysis, and reflect the ability of ICT systems to have a positive impact on patient care by supporting physicians in achieving their goals with a pleasant user experience. The research data incorporated 32 statements with a five-point Likert-scale on physicians' experiences on usability of their currently used ICT systems and a summative question about school grade given to electronic health record (EHR) systems. Physicians' estimates of their EHR systems were very critical. With the rating scale from 4 or fail to 10 or excellent, the average of the grades varied from 6.1 to 8.4 dependent on the kind of facility the physician is working. Questionnaire results indicated several usability problems and deficiencies which considerably hindered the efficiency of clinical ICT use and physician's routine work. Systems lacked the appropriate features to support typical clinical tasks, such as decision making, prevention of medical errors, and review of a patient's treatment chart. The systems also required physicians to perform fixed sequences of steps and tasks, and poorly supported the documentation and retrieval of patient data. The findings on ICT support for collaboration showed mainly negative results, aside from collaboration between co-located physicians. In addition, the study results pointed out physicians suffering from system failures and a lack of integration between the systems. The described study and related results are unique in several ways. A national usability study with nearly 4000 respondents had not been conducted in other countries in which healthcare technologies are widely adopted. The questionnaire study provided a generalized picture about the usability problems, however, it should be noted that there were significant differences between legacy systems in use. Previously, researchers had not approached contextual aspects of usability the context of clinical work, where numerous systems are in use. The described usability dimensions and the presented study results can be considered as the first step towards conceptualizing ICT usability in the unique setting of clinical work. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.