Sir,MicroRNAs is a new technology that is widely mentioned for application for blood product safety.[1] The concept is based on the molecular determination of MicroRNAs for various focused particles in blood products leading to identification of risk. Basically, the main function of individual MicroRNAs is modulating protein output from various genes.[2] The MicroRNAs can influence the biological processes of many cellular proteins in several pathways.[2] Hence, MicroRNAs takes important role in pathogenesis of many disorders including the infectious diseases.[2] At present, the issue of MicroRNAs is still in an early development phase.[1] Ryan and Atreya noted for the possibility of using MicroRNAs as a marker for safety of blood products.[1] This is based on the concept that expression profiles of MicroRNAs can be used as biomarkers for diagnosis of infectious diseases including those viruses of which diagnosis is difficult.[3] Indeed, there are some reports on success use of MicroRNAs as marker for several blood-borne infections such as hepatitis B, hepatitis C, and human immunodeficiency virus infections. Hence, there is a high probability for introduction of MicroRNAs as a new marker in transfusion medicine.However, there are some things to be discussed. In this correspondence, the author would like to raise concerns regarding the cost of investigation and feasibility of using microRNA as biomarkers. First, the cost of the investigation might be a big barrier for actual usage in transfusion medicine practice. As a new kind of biomarker, Lorenz noted that cost, feasibility, and reproducibility (ethnic variability) were important hurdles to be considered.[4] The cost for implementation of the system might be high and might not be affordable for some settings. Second, not all conditions can be detected by using MicroRNAs. The problems without RNA can still be existed. The examples are problematic unwanted chemicals in blood product. In conclusion, there might still be raised questions relevant to the on-going development of microRNA technology. Nevertheless, MicroRNAs will play important role in transfusion medicine practice in near future.