OBJECTIVES: Little is known about how resource utilization in the initial treatment period among advanced stage PCa patients differs between those receiving versus those not receiving chemotherapy, even for docetaxel, the earliest approved agent for metastatic disease. METHODS: We analyzed patients aged 66 or older from the linked Surveillance, Epidemiology, and End Results & Medicare (SEER-Medicare) database. Patients were diagnosed with PCa between 2000 and 2005 and were followed until censoring. We restricted the cohort to patients with incident Stage IV disease (AJCC-TNM classification) and at least 24 months of post-diagnosis follow-up data.  Initial costs (Medicare payments) were defined as costs incurred from 2 months before diagnosis to 12 months post-diagnosis and patients were stratified according to whether they received chemotherapy, and subsequently, whether they received docetaxel. RESULTS: Application of the inclusion criteria resulted in 4,088 Stage IV PCa patients, of which 23% (N=933) reported chemotherapy. Among chemotherapy users, 63% (N = 592) received docetaxel-containing regimens. Initial costs totaled $78.3M while PCa-specific initial costs totaled $49.9M.  For the full sample (F), chemotherapy subsample (C), and no chemotherapy subsample (NC), the proportions of total costs attributed to PCa-specific inpatient costs (IC), non-PCa-specific IC, PCa-specific outpatient costs (OC), non-PCa-specific OC, and other costs were distributed as follows: 1) PCa-specific IC: F=26.5% [$20.7M]; C=23.4% [$4.7M]; NC=27.5% [$16.0M]  2) non-PCa-specific IC: F=12.3% [$9.7M]; C=10.3% [$2.1M]; NC=13.1% [$7.6M] 3) PCa-specific OC: F=35.9% [$28.1M]; C=42.1% [$8.5M]; NC=33.8% [$19.6M]  4) non-PCa-specific OC: F=20.8% [$16.3M]; C=22.5% [$4.5M]; NC=20.1% [$11.7M]  and 5) Other costs: F=4.5% [$3.5M]; C=1.7% [$0.3]; NC=5.5% [$3.2M]. The proportion of PCa-specific outpatient costs was higher in the docetaxel subsample compared to the chemotherapy subsample. CONCLUSIONS: Among patients diagnosed with advanced disease, PCa-specific inpatient and outpatient costs accounted for two-thirds of Medicare payments, with PCa-specific outpatient costs gaining larger shares in the chemotherapy and docetaxel subsamples.