The introduction of computerized information systems into health care practices may cause changes to the way healthcare workers conduct their routine work activities, such as work flow and the time spend on each activity. To date the available work measurement tools are confined to activities in hospitals and do not cover residential aged care facilities (RACFs). There is little evidence about the effects of technology on caregivers' work practices, including the distribution of time on activities in a RACF. This requires the measurement of caregivers' activities using a valid and reliable measurement tool. The contribution of this research is to develop and test such a tool. The tool was developed based on literature research and validation in two RACFs. The final instrument contains 48 activities that are grouped into seven categories. They include direct care, indirect care, communication, documentation, personal activities, in-transit and others. This measurement tool can be used to measure the changes in caregivers' work activities associated with the introduction of computerized information systems in RACFs, including the efficiency gains of such systems.