Purpose To define patient characteristics associated with hospice enrollment in the last 3 days of life, and to describe adjusted proportions of patients with late referrals among patient subgroups that could be considered patient-mix adjustment variables for this quality measure. Methods Electronic health record–based retrospective cohort study of patients with cancer admitted to 12 hospices in the Coalition of Hospices Organized to Investigate Comparative Effectiveness network. Results Of 64,264 patients admitted to hospice with cancer, 10,460 (16.3%) had a length of stay ≤ 3 days. There was significant variation among hospices (range, 11.4% to 24.5%). In multivariable analysis, among patients referred to hospice, patients who were admitted in the last 3 days of life were more likely to have a hematologic malignancy, were more likely to be male and married, and were younger (age < 65 years). Patients with Medicaid or self-insurance were less likely to be admitted to hospice within 3 days of death. Conclusion Quality measures of hospice lengths of stay should include patient-mix adjustments for type of cancer and site of care. Patients with hematologic malignancies are at especially increased risk for late admission to hospice.