ABSTRACT. Drought stress is one of the most important factors limiting soybean [Glycine max (L.) Merr.] productivity and reducing yield stability. Soybean breeders need phenotypic and genotypic tools to improve drought stress tolerance, but most of available strategies are expensive and unaffordable for small-scale public breeding programs. In this study, elite germplasm of a locally adapted breeding population was used to estimate a yield stability index as an indicator of drought response.