Technical Abstract: Leaf rust (caused by Puccinia triticina) is one of the most important diseases of wheat in Uruguay, therefore breeding for resistance to this disease has been a long term objective for INIA wheat breeding program. Information of the identity of resistance genes present in the program is required to design strategies to breed for effective and more durable resistance. The leaf rust resistance genes present in seven adapted cultivars which have been extensively used in crosses were studied using different approaches. Isolates of Puccinia triticina with different virulence combinations were used to postulate seedling resistance genes in six cultivars. Genetic analysis of seedling and adult plant resistance (APR) was conducted on BC1F2 and F3 generations of four cultivars derived from crosses with the susceptible cultivar Thatcher and the presence of APR genes Lr13 and Lr34 was confirmed with intercrosses of Thatcher lines with these genes. A genetic marker associated with gene Lr34 was used to postulate the presence of this gene in all studied wheat cultivars. The cultivar Estanzuela Tarariras had Lr3bg ,Lr13 and Lr34; INIA Boyero had Lr26, Lr13 and Lr34; Estanzuela Benteveo had Lr3a and Lr13; Estanzuela Pelón 90 had Lr1, Lr17a, Lr26 and Lr34; INIA Caburé had Lr24; INIA Churrinche had Lr10 and Lr24; and INIA Tero had Lr17a and Lr24. INIA Boyero and Estanzuela Benteveo carry additional APR gene(s) that might be useful sources of resistance in addition to Lr34.