Medical alerts in CPOE are overridden in most cases. The need for alerting systems that are better adapted to physicians' needs and work processes is recognized. Our study aims to shed some light on how medical alerts are used and how they are integrated in the work process. Work analysis and interviews resulted in a hierarchical task analysis of prescription during ward rounds at the University Hospitals of Geneva. The results indicate that non-modal medical alerts are appreciated as an "insurance" for drugs that are out of the routine set. In the case of drugs that are often prescribed, alerts are ignored as physicians feel comfortable prescribing them. Non-interrupting alerts do not cognitively overcharge physicians, but the question is how to display the numerous alerts so that they are easily accessible when needed. Further, inexperienced physicians lack a mental representation of what evaluations the system is doing with the prescriptions and when alerts are triggered. This may lead to lack of trust or overconfidence, both of them potentially harmful.