Background: Germ cell tumors (GCT) account for 1% of malignancies of American males. Cisplatin combination chemotherapy is the cornerstone for curative therapy in metastatic GCT. Cisplatin is administered for 5 consecutive days, and it is appropriately categorized as highly emetogenic chemotherapy (HEC). Clinical and basic research over the past 25 years has led to steady improvements in the control of chemotherapy-induced nausea and vomiting (CINV). All of the guidelines (ASCO, MASCC and NCCN) unanimously suggest a combination of a 5-HT3RA, dexamethasone, and aprepitant for the prevention of acute and delayed CINV with single day HEC. However, there is paucity of studies and no clear guidelines evaluating multiday cisplatin-induced nausea and vomiting compared to single day cisplatin. We have published a randomized double-blind phase III trial testing whether the addition of aprepitant to standard 5HT3RA plus dexamethasone would provide additional protection in this patient population. Aprepitant was given for 5 consecutive days, starting on day 3 of chemotherapy; aprepitant 125mg PO (or matched placebo) was given on day 3, then 80mg PO on days 4-7. The complete response rate (CR) was 42% in the aprepitant arm vs. 13% in the placebo arm (p<0.0001), 80% of patients experienced no emetic episodes on days 1-5 on the aprepitant arm vs. just 52% on the placebo arm (p<0.0001).(J Clin Oncol. 2012 Nov 10;30(32):3998-4003. doi: 10.1200/JCO.2011.39.5558.) Methods: The current study is a single arm phase II study to evaluate the efficacy of combining fosaprepitant with a 5HT3RA + dexamethasone. This is the first clinical trial evaluating fosaprepitant in patients receiving multiday cisplatin. The primary objective is the Complete Response (CR) rate (no emetic episodes or use of rescue medications). Secondary objectives are the incidence of vomiting or retching via patient log and the patient’s self-reported assessment of nausea Days 1-8 using a 0-100mm visual analog scale (VAS). Clinical trial information: NCT01736917.