Understanding the context and nuances of clinical performance at the front-line can provide valuable insights into why the effects of Health Information Technology implementation might differ across sites. It also helps to inform the design of systems that support performance flexibility as clinicians respond to the changing demands of the clinical environment. This study explored the use of an electronic result acknowledgement (eRA) system by physicians at two Emergency Departments (EDs) at Australian metropolitan teaching hospitals to understand how electronic result acknowledgement is managed differently in response to varying environmental demands. Semi-structured, in-depth interviews relating to physician electronic test result acknowledgement processes were conducted with 21 emergency physicians. Physician use of the eRA system differed in four aspects: i) responsibility (i.e. who acknowledges test results); ii) types of tests acknowledged; iii) coordination and synchronisation (i.e. when acknowledgement occurred); and iv) documentation of follow-up actions.