As the expression pattern of microRNAs (miRNAs) present in blood changes in response to different disease states, we studied them to obtain information on the molecular mechanism of cardioembolic stroke pathogenesis involving CD46. miRNAs are a class of short (18–22 nucleotides), endogenously expressed, non-coding RNAs that act as riboregulators of gene expression [12], [13]. The gene discussed is CD46; the disease is cardioembolic stroke.