INTRODUCTION: Vault RNA1-1 (vtRNA1-1) exhibits antiviral and anti-apoptotic effects in infected and malignant cells. We observed that vtRNA1-1 levels in serum fluctuate in patients with hematological disorders, but its extracellular functions remain unclear. This study evaluates the potential of serum vtRNA1-1 levels as a biomarker for hematological disorders and investigates its association with bone marrow cell density (BMC). METHODS: Blood and serum samples were collected from patients with hematological disorders, patients who underwent bone marrow examination, PBSCT donors, and AML patients who received chemotherapy. VtRNA1-1 levels were measured using real-time quantitative RT-PCR. BMC was calculated by digital image analysis, and multiple regression analysis was performed using serum vtRNA1-1 and hematological and biochemical data as explanatory variables. RESULTS: The vtRNA1-1 levels in the blood of 11 patients with hematological disorders averaged 10.8 log CONCLUSIONS: Our findings suggest that serum vtRNA1-1, derived from peripheral blood and bone marrow cells, can potentially serve as a clinical biomarker in specific diseases.