In both mitotic and meiotic processes, cellular surveillance of the integrity of genetic information transmission from parental cells to their subsequent generations is carried out by a network of proteins primarily involved in cell-cycle regulation, DNA replication, DNA repair, and chromosome segregation. Within this context, the mammalian MRE11 represents an essential multifunctional protein that promotes repair of DNA double-strand breaks and plays a role in the signaling of DNA damage response. Mutations in human hMRE11 gene could contribute to the rare "AT-like" disorder. However, at present time the functional roles of hMRE11 in these cellular processes are elusive. In the current study, we provide evidence that hMRE11 interacts physically with the mismatch repair protein hMLH1 through yeast two-hybrid analysis. In addition, we show that recombinant hMRE11 and hMLH1 proteins interact when these two proteins are coexpressed in bacterial cells, and both proteins can be co-immunoprecipitated from human cell extracts. Furthermore, hMRE11 and hMLH1 display similar expression patterns when examined with a human normal/tumor DNA array. Together, these data suggest that hMRE11 and hMLH1 might act in a co-operative fashion during DNA damage detection, signaling, and repair.