The medication administration stage of the medication-use process is especially vulnerable to error because errors are least likely to be caught before reaching the patient. Medication administration, however, remains poorly understood. In this article we describe medication administration as observed in an ethnographic study conducted on one medical unit and one surgical unit. A central finding was that medication administration entailed a complex mixture of varied and often competing demands that temporally structured the nurses' entire workday. Articulation work was evident in time management strategies nurses used to handle demands from institutional policies, technical devices, patients, the physical environment, and the medications themselves. The average number of doses of medication per patient was more than double the number policy groups have indicated. Medication administration is not simply the giving of drugs, nor does it have clearly defined temporal boundaries. Because of its inseparability from other nurses' work, medication administration inherently entails interruption, thereby calling into question the current emphasis on reducing interruptions as a tactic to decrease medication errors.