The wheat leaf rust resistance gene LrCen was first identified in the Thatcher-Lr1 near-isogenic line RL6003. In crosses between RL6003 and Thatcher the Lr1 and LrCen genes segregated independently. There are only a small number of Puccinia triticina Eriks. virulence phenotypes that are avirulent to LrCen but these include some of the most common virulence phenotypes found in Canada during recent annual virulence surveys, such as TDBG. These virulence phenotypes also have unusual avirulence to the Lr14a and Lr20 Thatcher near-isogenic lines. Allelism tests between LrCen and both Lr14a and Lr20 demonstrated that LrCen was not allelic to either of these genes. It was however allelic to a seedling resistance gene in the otherwise susceptible line, Little Club. LrCen has an unusual phenotypic response and when TDBG was used to inoculate a large and diverse set of Canadian wheat lines, many appear to have this gene. Research is underway to map and genetically characterize this unusual leaf rust resistance gene.