The advent of fast-acting drugs has made the infusion pump the most pervasive medical device in the acute care (hospital) environment and its correct operation is critically important. U.S .Food and Drug Administration (FDA) database incident reports implicate interface programming as a significant aspect of adverse outcomes. This article describes a study of infusion pump programming performance by healthcare professionals at a major urban teaching hospital. Early findings indicate that practitioner experience with device programming does not increase proficiency. This suggests that interface menu structure (“menuspace”) makes programming difficult and inefficient and impedes practitioners from the development of mental models that are sufficient to operate the devices, This causes many to become disoriented, or lost, in the interface. We relate these findings to current study of the USFDA adverse events reports and indicate directions for further research.