Since August 1996, the oncology clinicians at Massachusetts General Hospital (MGH) have been using an in-house developed CPOE system to order chemotherapy for their adult population. While the pediatric chemotherapy ordering remained on paper until November 2003, designing the pediatric chemotherapy functionality into the existing CPOE product proved to be very challenging. It was helpful in one sense because there was an existing framework that was familiar to everyone. It was also restrictive, in the sense that it is hard to enhance it without impacting others already using the same system.