Objective: To evaluate the impact of an electronic drug monitoring system (eDMS) for ambulatory rheumatology patients on time nurses spent on, and the process of, drug monitoring. Methods: The study was conducted in the Rheumatology Department of a large metropolitan hospital. The eDMS, a module of the Hospital Clinical Information System (HCIS), was designed to allow electronic ordering and subsequent monitoring of ambulatory patients on long-term, immunosuppressive rheumatology medications. Quantitative measures collected before and after the intervention were: time spent on specific nursing activities; who nurses spent time with; format and location of documentation monitoring; and patient throughput. Qualitative data from interviews and observations were collected to ascertain the impact of the eDMS on nurses' monitoring activities. Results: Nurses spent significantly less time on medication monitoring tasks (33.1% versus 26.4%, P=. 0.003) and significantly more time on patient care (6.5-18.1%, P<0.0001) following implementation of the eDMS. Nurses also spent significantly more time with patients (7.7-19.8%, P<0.0001) and relatives (0.4-3.7%, P=. 0.01) after the system was implemented. The time saved on monitoring allowed the number of nurse directed clinics and patient throughput to increase following eDMS implementation. Qualitative data supported results from the timing study with nurses reporting that the monitoring process was more standardised, safer, took less time and simplified documentation. Conclusions: The eDMS was associated with a reduction in time spent on the complex task of medication monitoring allowing nurses to spend a greater proportion of their time on other patient care activities.