 The review highlights the involvement of abstract microRNAs, myrnas, in drug resistance in cancer chemotherapy, which is a major obstacle to curing this disease. Over 90% of cancer mortality is related to drug resistance, and myrnas are found to be involved in this process by targeting drug resistance-related genes or influencing cell proliferation, cycle, and apoptosis. The regulatory effect of a single myrna on multiple genes is tissue-specific, and the mechanisms of deregulated expression of myrnas are explored comprehensively. The molecular targets and underlying signalling pathways of myrnas in drug resistance are also examined, with the aim of developing better strategies to regulate them efficiently for use in cancer therapy. This article was authored by Wen Gong Si, Zhou Yingshan, Wei Linxian, and others.