OBJECTIVES:  Cost-of-care information in ED-SCLC is limited. Most studies include only treated patients and do not provide costs over time or by chemotherapy status. This study was designed to quantify total direct medical costs 90 days and 1 year post-diagnosis for a cohort of US Medicare patients with ED-SCLC (overall and according to receipt of outpatient chemotherapy within 90 days of diagnosis). METHODS: Using Surveillance, Epidemiology, and End Results (SEER) data linked to Medicare claims, we identified patients aged ≥66 years with Medicare Parts A and B coverage and a first primary, ED-SCLC SEER diagnosis (pathologically confirmed) between 1/1/2007 and 12/31/2011. Patients were followed from diagnosis until death, second primary cancer, coverage change, or 12/31/2013. Treatment was determined using Medicare claims. Medicare-paid amounts were adjusted to 2013 US dollars using the Consumer Price Index medical component. Cumulative incremental direct medical costs were estimated, accounting for censoring with bootstrapped confidence intervals (CI). RESULTS: In our cohort of 5498 patients with ED-SCLC, mean age was 75 years (range: 66-98), 49% were male, and 86% were white. Median survival time for all patients was 4.7 months. Mean cumulative incremental cost per patient was $29,213 (95% CI: $28,589-$29,838) at 90 days and $50,206 (95% CI: $49,151-$51,260) at 1 year. Hospitalizations accounted for 56% of first-year costs. Of 3014 patients initiating outpatient chemotherapy within 90 days of diagnosis, 87% received platinum/etoposide. Mean costs were higher for chemotherapy-treated patients than untreated patients (n=2484) 90 days post-diagnosis ($30,182 [95% CI: $29,464-$30,901] vs $27,949 [95% CI: $26,877-$29,022]) and 1 year post-diagnosis ($61,532 [95% CI: $60,187-$62,877] vs $36,068 [95% CI: $34,585-$37,550]). CONCLUSIONS:  A substantial portion of first-year costs for patients with ED-SCLC were incurred within 90 days of diagnosis. First-year costs were higher for patients initiating outpatient chemotherapy within 90 days than for untreated patients. Novel therapies could affect costs by reducing hospitalizations.