Previous studies of hereditary nonpolyposis colorectal cancer (HNPCC) patients using QF-PCR or Southern blotting have detected hMLH1 and hMSH2 copy number variants in 5% of probands in Germany (Wang et al, 2003), 5% in Japan (Nakagawa et al, 2003), 15% in France (Charbonnier et al, 2002) and 27% in the USA (Wagner et al, 2003). This evidence concerns the gene MSH2 and hereditary nonpolyposis colon cancer.