The incidence of human immunodeficiency virus (HIV)-associated primary central nervous system lymphoma (PCNSL) has decreased in the era of highly active anti-retroviral therapy, but PCNSL continues to be a prominent AIDS-defining illness. Using surveillance epidemiology and end results, cancer registry data linked with Medicare, we identified PCNSL cases diagnosed from 1994 to 2002. The effects of comorbidity, year of diagnosis, and sociodemographic characteristics on the odds of receiving treatment were assessed. One hundred and eighty-four patients with both HIV and PCNSL were identified. Forty-six per cent were treated with radiation therapy (RT) alone, 10% received RT and chemotherapy, 4% received chemotherapy alone, and 40% received no treatment. No time trends in treatment patterns were observed, and no sociodemographic factors were associated with receipt of treatment. Median survival was 2 months. Age did not impact survival. Survival was improved for patients diagnosed with PCNSL after 1996 (p = 0.028). Despite improved treatment for both diseases over the past decade, survival remains dismal in this cohort of Medicare/Medicaid beneficiaries with HIV-related PCNSL. These results may not apply to the general HIV population.