Exosomes are small vesicles that are shed from almost all cell types under both physiological and pathological conditions. Recently, we and other groups show that exosomes carry secreted microRNAs (miRNAs) into recipient cells and affect their function. Here, we report studies of miRNA profiles in exosomes derived from cell lines of human embryonic kidney (HEK293T) and Lewis lung carcinoma (LLC). Our results reveal that miRNA profile are largely different in those two.type of exosomes Among miRNAs contained in LLC exosomes, many oncomiRs are up-regulated significantly and tumor suppressor miRNAs are down-regulate dramatically Further study shows that it only has a increased level of trasfected miRNA/RNAi, but no alteration of the origin miRNA and protein in exosome by transfecting of thiere mimic into HEK293T cells.. Taken together, these results indicate that exosome miRNAs have cell-type specificity. Exosome also serves as new type of carrier to deliver miRNAs into target cell/tissue for therapy.