PURPOSE: To test the hypothesis that miR429 expression in renal cancer patients is increased and plays a role in the pathogenesis of the disease. METHODS: Twenty-seven renal cancer patients admitted to our hospital from May 2014 to May 2015 were enrolled as the study group, and 28 non-cancer patients were selected during the same period as the control group. Renal biopsy and serum samples were used to detect miR429 expression levels, and the patient histories were obtained to make relevant associations to clinical outcomes. In addition, the renal cancer cell line SK458 was used for overexpressing or knocking out miR429 in in vitro experiments to observe changes in proliferation and apoptosis rates. RESULTS: The expression levels of miR429 in renal tissues and serum of renal cancer patients were significantly higher compared with control patients (p<0.05). In addition, a correlation was found between the levels of miR429 in the serum of renal cell cancer patients and their clinical outcome after conventional treatment, with patients expressing lower miR429 levels showing better clinical outcomes. Finally, experiments with renal cancer cells revealed that the proliferation of cells overexpressing miR429 was increased and their apoptosis rate was significantly reduced, while the opposite was true in miR429-knockout cells. CONCLUSIONS: It seems that miR429 can inhibit normal apoptosis rates and lead to high proliferation rates. Accordingly, the higher serum miR429 level in renal cancer patients suggests that it plays a role in the pathogenesis of the disease, while the differential miR429 levels according to the patients' clinical outcomes after treatment suggest that miR429 may be useful as a marker for prognosis.