Durable disease resistance is necessary for sustainable wheat production. Wheat lines with resistance to stem rust at the adult plant stage, but susceptible as seedlings, have been under selection as a proxy for durable resistance since racespecific adult plant resistance to stem rust has not been documented to date. We identified 27 wheat lines that possessed susceptible seedling reactions to wheat stem rust pathogen races TTKSK, TKTTF, and TRTTF. In order to determine if any of these lines possessed race-specific adult plant resistance,t he lines were evaluated in single-race field nurseries at Kulumsa, Ethiopia in2014 and 2015. The majority of resistant lines possessed similar responses to the three races, but two lines showed race-specific coefficient of infection values that were confirmed by significant differences in plot yield and thousand kernel weight. These two wheat lines were resistant to TTKSK, but susceptiblet o TKTTF. In a separate study, we detected a QTL for adult plant resistance to stem rust derived from cultivar ‘Morocho Blanco’ on chromosome arm 6AS that was effective to the Ug99 race group in Kenya (2013-2015 data), but was not effective to two North American races in single-race field nurseries in Minnesota in 2015 and 2016. To determine if the observed QTL was specific to pathogen races or environments, we tested the parents of the mapping population for adult plant response to three stem rust pathogen races in a growth chamber. Morocho Blanco and susceptible parent ‘LMPG-6’ were both seedling susceptible to the races TTKSK, TKTTF, and RCRSC. At the adult plant stage, Morocho Blanco displayed resistant infection responses to race TTKSK, but susceptible responses to races TKTTF and RCRSC across three repeated experiments. These data indicate the presence of race-specific adult plant resistance to wheat stem rust. The genetics of race-specific adult plant resistance may be conferred by a single QTL in Morocho Blanco.