We investigated a possible role of the mismatch-repair gene MLH3 in heredit
ary nonpolyposis colorectal cancer by scanning for mutations in 39 HNPCC fa
milies and in 288 patients suspected of having HNPCC. We identified ten dif
ferent germline MLH3 variants, one frameshift and nine missense mutations,
in 12 patients suspected of HNPCC. Three of the 12 also carried a mutation
in MSH6.