Leaf rust (caused by Puccinia triticina Eriks.) is an important disease of wheat (Triticum aestivum L.) in Uruguay; therefore breeding for resistance to this disease has been a long-term objective for the INIA wheat-breeding program. Information on 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 that have been extensively used in crosses were studied. Races of Puccinia triticina with different virulence combinations were used to determine which seedling resistance genes may be present in six cultivars. Genetic analysis of seedling and adult plant resistance (APR) was conducted on BC 1F 2 and F 3 generations from four cultivars crossed with the susceptible cultivar Thatcher. The cultivar Estanzuela Tarariras was postulated to have Lr3bg and genetically determined to have Lr13 and Lr34; INIA Boyero was postulated to have Lr26 and genetically determined to have Lr13 and Lr34; Estanzuela Benteveo was postulated to have Lr3a and Lr26 and genetically determined to have Lr13. Estanzuela Pelón 90 was postulated to have Lr1, Lr17a, and Lr26 and genetically determined to have Lr34; INIA Caburé was postulated to have Lr24; INIA Churrinche was postulated to have Lr10 and Lr24; and INIA Tero was postulated to have Lr17a and Lr24. INIA Boyero and Estanzuela Benteveo carry additional APR gene(s) that might be useful sources of resistance in addition to Lr34.