Quantitative trait loci (QTL) mapping for yield in soybean [Glycine max (L.) Merrill] plant introductions (PIs) could broaden the soybean germplasm base in the US. The objectives of our study were to map QTL for yield and other agronomic traits, and to determine QTL x environment and epistatic interactions for yield in three backross (BC) populations developed by crossing soybean lines derived from PIs with Beeson 80, Kenwood and Lawrence. Sixty-eight BC₂F₆-derived lines in the Beeson, 74 BC₁F₆-derived lines in the Kenwood and 94 BC₃F₃-derived lines in the Lawrence populations were evaluated as separate experiments along with the domestic parents and checks in 2003 and 2004. A total of 45 polymorphic simple sequence repeat (SSR) markers was used to genotype the Beeson, 84 in the Kenwood and 30 in the Lawrence populations. Thirteen yield QTL and 19 QTL for three agronomic traits were identified across the three populations. Eight yield QTL were derived from the PI parents. Three yield QTL were associated with delayed maturity, one with more lodging and increased plant height. The 13 yield QTL mapped to regions where yield QTL have been reported. Only one yield QTL showed consistent effects across environments. The QTL x environment interactions were due no or weak QTL effect and variation in the magnitude of QTL effects. A total of nine epistatic interactions for yield was detected in the Kenwood population mostly between loci exhibiting epistatic effects only. Our results support previous findings that the current commercially used soybean gene pool is more diverse than would have been predicted by the number of contributing ancestors. Additional studies involving different PIs will be important to expand the search for unique yield enhancing alleles that are not present in the US soybean cultivars.