64 kidney tumours of clear cell histopathology were analysed with non-isotopic SSCP and HA for the presence of VHL gene defects. All positive cases were further characterised by direct sequencing. In 30 tumours (48%) mutations were identified in the coding region of the VHL gene. Other tumours were examined for methylation changes in 5' CpG islands in exon 1 Bisulphite genomic sequencing which gives positive signal for methylated cytosines, was used in this analysis and in 7 tumours hypermethylation of 5' CpG islands was found. These findings suggest that VHL gene mutations together with methylation associated inactivation of the VHL gene are important events that predispose to renal cell tumorigenesis.