Background: The goal of post-treatment surveillance of CRC patients is to identify recurrences among patients eligible for salvage surgery or palliative chemotherapy. However, patient ineligibility for treatment of recurrence may contribute to variation in surveillance practices. The aim of this study was to evaluate patient factors that affect clinician decisions regarding surveillance and salvage treatment eligibility among CRC patients. Methods: A custom 41-item survey was developed, incorporating modified criteria for adult comorbidity evaluation. A convenience sample of physicians who treat CRC was recruited from the ALLIANCE GI Cancer Committee. All participants completed an anonymous written survey of objective and subjective information about salvage treatment eligibility and the impact on surveillance in these patients. Results: Respondents were medical oncologists (n = 16; n = 11 with > 10 yrs experience) and surgical oncologists (n = 4). Patients with average comorbidity were considered ineligible for curative salvage surgery at median age 85 yrs (IQR: 80, 90), life expectancy 3 yrs (IQR: 2, 4.8) or ECOG ≥ 2 (IQR: 2,3). Patients were considered ineligible for palliative chemotherapy at median age 90 (IQR: 80, 92.5), life expectancy ≤ 2 years (IQR: 1.5, 3) or ECOG status ≤ 3 (IQR: 3, 3). Patients with above average comorbidity were considered ineligible for salvage surgery at median age 80 yrs (IQR: 75, 80) and palliative chemotherapy at median age 80 yrs (IQR: 75, 85). 8 comorbidities were identified by > 75% of the respondents as determinants of treatment ineligibility. 12 respondents (60%) indicated follow-up of patients ineligible for treatment should be continued based on patient desire, ongoing management of late effects, and continuity of care. However, a majority (n = 15) responded that clinic visits only should be continued without further testing. Conclusions: Considerable agreement was observed regarding patient characteristics that lead to ineligibility for treatment of recurrent disease. This information can aid shared clinical decision-making for post-treatment surveillance strategies and may potentially reduce variation in surveillance practice.