Soybean [Glycine max (L.) Men.] oil from conventional cultivars typically contains -30 g kg-'' stearic acid of the total seed oil. Increased stearic acid concentration in the seed oil of soybeans is desirable for certain food and industrial uses. To date a small number of mutants have been developed with increased stearic acid levels three to six times that of normal. At least two such lines were found to possess separate mutations in the delta-9-stearoyl-acyl carrier protein desaturase C gene {SACPD-C) that dramatically increased seed stearic acid concentration. We now report additional independent mutations in this gene that increase seed stearic acid levels of the soybean germplasm line RG7 to -116 g kg"''. An Fg recombinant inbred line (RIL) population was developed to determine the relationship between the RG7 SACPD-C mutation and stearic acid concentration. Transgressive segregation in the progeny of the cross between mutant lines RG7 and RG2 (low palmitic acid) further increases seed stearic acid to almost 180 g kg-^, suggesting the presence of yet another gene having a significant effect on stearic acid accumulation. We also discerned an independent, presumably allelic, mutation within the SACPD-C gene in line RG8, which has about 106 g kg '' stearic acid. Molecular markers diagnostic for the RG7 and RG8 SACPD-C mutations were developed, enabling rapid selection for these mutations in the development of cultivars with increased seed stearic acid content in the seed oil.