Abstract： Objective To explore the characteristics of hemi-nested methylation specific polymerase chain reaction (hn-MSP) and to find out the possible relationship between patterns of methylation or deletion and the developmet of adult acute lymphoblastic leukemia(ALL).Methods hn-MSP and bisulfit-sequencing PCR (BSP) were designed and adopted to analyze p15 gene methylation or deletion patterns in 25 adult ALL patients,malignant hematopathy cell lines and normal lymphocytes. hn-MSP and BSP products were cloned and sequenced.The sensitivity and specificity of hn-MSP were also analized.Results The sequencing results of hn-MSP and BSP products were consistent, and the sensitivity of detection of p15 methylation was up to 1.0×10-5.17 adult ALL patients (68 ％) were p15 gene hypermethylation and 3 patients were with deletion of p15 gene exon 1.There were no hypermethylation or deletion in the 10 controls.Conclusions The detection rate of p15 methylation in many tumors,especially in adult ALL,is frequent high.hn-MSP is highly sensitive and specific in analyzing p15 methylation.