Technical Abstract: Previous research identified soybean accession PI 567099A as resistant to soybean rust (SBR). The objective of this research was to map the resistance genes(s) of PI 567099A. A population segregating for SBR resistance was evaluated in the 2008 and 2009 seasons in Paraguay. In both seasons F2:3 families were grown in a field naturally infested with SBR. Each F2:3 family was rated as resistant, segregating, or susceptible on the basis of the lesion types present and this classification was used to infer the F2-phenotype used for mapping. For the 91 F2:3 families rated in 2008, segregation did not fit a 1:2:1 (resistant:segregating:susceptible) ratio expected for a single gene (P<0.05). However, for the 68 families rated in 2009, segregation fit a 1:2:1 ratio very well ('2 =0.7059, P = 0.7026). Molecular markers flanking five major SBR resistance genes were applied to the F2 population and despite the discrepancy in segregation ratio between years, markers flanking Rpp3 where significantly associated with the observed resistance (P<0.0001) in both years. Analysis of allele frequencies in homozygous F2:3 families in 2009 confirmed an association with Rpp3. However, the phenotype of 24-F1 plants evaluated in the 2008 season indicated that the resistance was recessive. This is the first report of recessive resistance at or near the Rpp3 locus. Knowledge of the location and nature of resistance in PI 567099A will allow its more efficient utilization as a SBR resistance source in breeding programs.