Technical Abstract: Maize susceptibility to ear rot and aflatoxin accumulation by Aspergillus flavus has caused significant economic losses for farmers in the United States over the past 30 years. Aflatoxin outbreaks are generally associated with high temperatures and low moisture levels common to the southern US. To identify aflatoxin accumulation resistance Quantitative Trait Loci (QTL) and linked markers for marker assisted breeding, a genetic mapping population of F2:3 family genotypes, increased by sib-mating, was developed from Mp717, a maize inbred resistant to aflatoxin accumulation, and NC300, a southern adapted inbred with low levels of resistance and desirable agronomic traits. Replicated trials of the mapping population were subjected to A. flavus inoculation in Tifton, GA and Starkville, MS in 2004 and 2005. QTL on all chromosomes except 2 and 6 were identified, and individual QTL explained from less than 1% to a maximum of 15% of the phenotypic variance in aflatoxin accumulation in grain. Both Mp717 and NC300 were found to contribute resistance to aflatoxin accumulation, and overall QTL effects differed due to environmental conditions. Many of these loci are distinct from previously identified QTL, which confirms Mp717 as a novel source of aflatoxin resistance.