Background: Quality end-of-life cancer care involves a shift from aggressive therapy to supportive services.   Reasons for variations in intensity of late-life cancer care are incompletely understood.  The goal of this work was to examine intensity of care based on principal healthcare provider in the last month of life, comparing primary care providers (PCPs) with oncology specialists. Methods:  A retrospective claims-based analysis of hospitalizations, emergency department (ED) visits, intensive care unit admissions in the last 30 days of life; in-hospital deaths; terminal chemotherapy; and under-use/late hospice referrals among a 20% sample (n=235,821) of Medicare beneficiaries dying with poor-prognosis cancers. Logistic regression was used to quantify care variations comparing PCPs with oncology specialists as well as combined care by PCPs and oncology specialists Results: Among the 235,821 individuals studied, mean age at death was 78 years, 51.4% were male, 90.8% were non-black race, 73.5% lived in urban areas, and median income was $46,634.  Of these, 74% received care from a PCP and/or an oncology specialist in the last month of life.  Data (expressed as %) comparing the full cohort with those principally cared for by PCPs versus by oncology specialists versus combined care by PCPs and oncology specialists follow. Conclusions:  Most measures of care intensity fell outside published benchmarks, signifying overly aggressive care.  Intensity of late-life care among cancer-affected seniors varies significantly by principal healthcare provider with the most intensive care shown among those receiving combined care from PCPs and oncology specialists.