Electronic health record (EHR) implementation can be associated with both risks and improvements in safety. This study sought to characterize the positive and negative safety implications of EHR implementation and ongoing use by analyzing interview data from a 30-month evaluation of EHR implementation at 12 sites in the United Kingdom's National Health Service. The study demonstrates how eight specific human–technological factors in a sociotechnical model (people, workflow and communication, internal organizational features, external rules and regulation, measurement and monitoring, hardware and software, clinical content, human–computer interface) come into play in moving health care organizations through three phases of technology implementation. Safety hazards may be introduced in early phases of EHR implementation phases, and inappropriate use of technology as implementation progresses can also result in risks. When EHR use has stabilized, the technology can be used to promote safety.