Background： DNA hypomethylation of long interspersed nuclear elements- 1 （LINEs- 1 ） occurs during carcinogenesis, whereas intbmaation addressing LINE-1 methylation in Wilms tumor （WT） is limited. The main purpose of our study was to quantity, LINE-1 methylation levels and evaluate their relationship with relative telomere length （TL） in WT. Methods： We investigated LINE-1 methylation and relative TL using bisulfite-polymerase chain reaction （PCR） pyrosequencing and quantitative PCR, respectively, in 20 WT tissues, 10 normal kidney tissues and a WT cell line. Significant changes were analyzed by t-tests. Results： LINE-1 methylation levels were significantly lower （P 〈 0.05） and relative TLs were sigmificantly shorter （P 〈 0.05） in WT compared with normal kidney. There was a significant positive relationship between LINE- 1 methylation and relative TL in WT （r = 0.671, P = 0.001 ）. LINE- 1 Methylation levels were significantly associated with global DNA methylation （r = 0.332, P 〈 0.01 ）. In addition, relative TL was shortened and LINE- 1 methylation was decreased in a WT cell line treated with the hypomethylating agent 5-aza-2＇-deoxycytidine compared with untreated WT cell line. Conclusion： These results suggest that LINE-1 hypomethylation is common and may be linked to telomere shortening in WT.