OVERVIEW: It is often an accepted practice that a 20-gauge-or-larger catheter is used for the safe transfusion of blood in adult patients, but it is unclear what evidence supports this practice. This article tells the story of how a small team of oncology nurses designed and implemented an evidence-based practice project to challenge that convention. A literature search and a consultation with the standards of the American Association of Blood Banks and the Infusion Nurses Society determined that a smaller-than-20-gauge catheter can be used safely to transfuse blood in adults, a discovery that led to a change in policy and practice at the authors’ institution.