The aim of this study was to investigate the unintended adverse consequences ofintroducing electronic health records (EHR) in residential aged care homes (RACHs) and toexamine the causes of these unintended adverse consequences.Method: A qualitative interview study was conducted in nine RACHs belonging to three orga-nisations in the Australian Capital Territory (ACT), New South Wales (NSW) and Queensland,Australia. A longitudinal investigation after the implementation of the aged care EHR sys-tems was conducted at two data points: January 2009 to December 2009 and December 2010to February 2011. Semi-structured interviews were conducted with 110 care staff membersidentified through convenience sampling, representing all levels of care staff who workedin these facilities. Data analysis was guided by DeLone and McLean Information SystemsSuccess Model, in reference with the previous studies of unintended consequences for theintroduction of computerised provider order entry systems in hospitals.Results: Eight categories of unintended adverse consequences emerged from 266 data itemsmentioned by the interviewees. In descending order of the number and percentage of staffmentioning them, they are: inability/difficulty in data entry and information retrieval, enduser resistance to using the system, increased complexity of information management, enduser concerns about access, increased documentation burden, the reduction of communi-cation, lack of space to place enough computers in the work place and increasing difficultiesin delivering care services. The unintended consequences were caused by the initial condi-tions, the nature of the EHR system and the way the system was implemented and used bynursing staff members.Conclusions: Although the benefits of the EHR systems were obvious, as found by our previ-ous study, introducing EHR systems in RACH can also cause adverse consequences of EHRavoidance, difficulty in access, increased complexity in information management, increaseddocumentation burden, reduction of communication and the risks of lacking care follow-up, which may cause negative effects on aged care services. Further research can focus oninvestigating how the unintended adverse consequences can be mitigated or eliminated byunderstanding more about nursing staff's work as well as the information flow in RACH.This will help to improve the design, introduction and management of EHR systems in this setting.