The patient-reported outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) complements capture of symptomatic adverse events (AEs) by clinicians. Previous trials have typically used a limited subset of relevant symptomatic AEs to reduce patient burden. We aimed to determine the feasibility of administering all 80 AEs included in the PRO-CTCAE library by approaching consecutive patients enrolled in a large academic phase I program at three points in time. Here, we report a preplanned analysis after enrolling the first 20 patients. All items were answered on 51 of 56 potential visits (adherence 91%). Three (5%) additional PRO-CTCAE assessments were partially completed, and two (4%) were missed because of conflicting appointments. No patient withdrew consent or chose not to complete the assessments once enrolled on study. Future trials of experimental drugs that incorporate the PRO-CTCAE should consider using this unselected approach to identify adverse events more completely.