Brain metastases are a frequent complication of many systemic cancers and portend a poor prognosis. This retrospective analysis of health claims data compared survival, treatment and health care utilization and costs in patients with brain metastasis by primary tumor site. Adult commercial and Medicare Advantage enrollees newly diagnosed with brain metastasis in 01 Jan 2004 through 30 Apr 2010 were identified. Inclusion required at least 2 claims that identified the same primary cancer site prior to diagnosis of brain metastasis and no evidence of primary brain tumors. Health care utilization rates and costs were calculated at the patient level for each month of follow-up. Differences among primary cancer site cohorts were assessed by ANOVA (continuous variables), Chi square test (proportions) and the Poisson distribution (utilization rates). The primary cancer cohorts comprised 1,031 lung cancer, 93 melanoma and 395 female breast cancer patients. During the 6 months prior to brain metastasis diagnosis, 59 % of lung cancer patients had no evidence of lymph node involvement or other metastatic disease compared to 55 and 42 % of melanoma and breast cancer patients (P < 0.001). Survival after brain metastasis diagnosis was less than 3 months for 52, 43 and 39 % for lung cancer, breast cancer and melanoma, respectively (P < 0.001). Melanoma patients had the highest rate of inpatient stays and outpatient visits (P ≤ 0.003). Total monthly all-cause costs were: melanoma, $23,426; breast cancer $19,708; lung cancer, $17,007 (P = 0.003). Health care utilization and costs after brain metastasis diagnosis were substantial and differed by primary tumor site.