Medication administration errors have been shown to be frequent and serious. Error is particularly prevalent in highly technical specialties such as critical care. The purpose of this study was to describe the characteristics of intravenous medication administration in five intensive care units. These data were used within the context of a larger study to design information system decision support in these settings. Nurses were observed during the course of their work and their intravenous medication administration process, order source, references used, calculation method, number of medications prepared simultaneously, and any interruptions occurring during the preparation and delivery phases of the administration event were recorded. In addition, chart reviews of medication administration records were completed and nurses were asked to complete an anonymous drop-box questionnaire regarding their experiences with medication administration error. The results of this study are discussed in terms of potential informatics solutions for reducing medication administration error.