DNA methylation in the promoter regions of the MGMT, NEIL1, ERCC1 and RAD23B genes was assessed in 56 NSCLC tumours using MS-HRM. Methylation was detected in MGMT (25%), NEIL1 (42%), ERCC1 (2%) and RAD23B (2%). The negative first derivative plots of representative methylated NSCLC tumours for MGMT (Panel A) and NEIL1 (Panel B), ERCC1 (Panel C) and RAD23B (Panel D) are shown. Bisulfite Sanger sequencing traces confirming the ERCC1 and RAD23B methylation status are shown below the negative first derivative plots. Red, green and blue asterisks indicate the positions of methylated cytosines, unmethylated cytosines and bisulfite conversion controls respectively.