Background: Patients (pts) with germ cell tumors (GCT) who fail to be cured following multiple chemotherapy (CT) courses (± high-dose CT) have an extremely poor prognosis and long-term remissions are anecdotal. Pazopanib (PZP) is a potent and selective, orally available, TKI of VEGFR1, 2, and 3, PDGFRα, PDGFRβ, and cKit. Here we report the initial results of the ongoing open-label, single-group, phase II study which is sponsored by INT Milano (ClinicalTrials.gov NCT01743482). Methods: Pts with refractory GCT received pazopanib 800 mg/day orally until disease progression or evidence of unacceptable toxicity/side effects. Eligibility requirements included failure of at least two platinum-based CT, including high-dose CT. All pts underwent measurement of serum tumor markers (STM), a computed tomography and a FDG-PET after one month of treatment and q2 months thereafter. Results: From May 2013 to July 2013, five pts were enrolled, three in fourth, and two in fifth-line. Median age was 39 (IQR: 33 to 48). Three out of five had failed high-dose chemotherapy (HDCT), two had an extragonadal primary, all pts had at least one elevated STM at baseline, the sole parameter in one patient, two had liver metastases, four pts had a retroperitoneal relapse. Four had elevation of alfafetoprotein (AFP), one of human choriogonadotropin (HCG). Four were nonseminomas, one a pure seminoma. After the first month of treatment, four out of five pts had a decrease in marker levels, one patient had disease progression (PD). Two of the responding pts had a necrotic evolution of disease at computed tomography corresponding to a RECIST and metabolic (PET/CT) progression, two had a stable disease. Two-month follow up is available for three out of four responders: one interrupted PZP for toxicity and had a marker PD, another an increase to baseline levels and the last one a further reduction (pure seminoma, one out of five confirmed response at two months). There were two cases of hepatic toxicities (one G2 and one G3-4 with dose interruption). Conclusions: PZP is endowed with preliminary activity in extensively pretreated patients with GCT. The unique availability of STM in interpreting densitometric and metabolic response might provide insights into response assessment of solid tumors under antiangiogenic therapy. Clinical trial information: NCT01743482.