American elm (Ulmus americana ) is a valuable and sentimental tree species that was decimated by Dutch elm disease in the mid-20th century. Therefore, any methods for modifying American elm or enhancing disease resistance are significant. This protocol describes transformation and tissue culture techniques used on American elm. Leaf pieces containing the midvein and petiole are used for explants. Agrobacterium tumefaciens strain EHA105 is used for transformation, with the binary vector pSE39, containing CaMV35S/npt II as a selectable marker, ACS2/ESF39A as a putative resistance enhancing gene, and CaMV35S/GUS as a reporter.