Objectives: Screening subjects for drug-drug interactions (DDI) prior to enrollment in oncology clinical trials is integral to ensuring safety, but standard procedures or tools are not readily available to screen DDI in this setting. Our objective was to develop a DDI screening tool for use during oncology clinical trial enrollment and to test usability in single-center and multi-center pilot studies.Methods: A multi-stage approach was utilized for this quality improvement intervention. Semistructured interviews with individuals responsible for DDI screening were conducted to develop a prototype tool. The tool was used for screening DDI in subjects enrolling in National Clinical Trials Network trials of commercially available agents during a single-center 3-month feasibility pilot. Improvements were made, and a 3-month multi-center pilot was conducted at volunteer