Technical Abstract: In this study, we present data characterizing the effects of soil moisture levels on total leaf conductance for two distinct determinate soybean (Glycine max (L.) Merr.) genotypes and subsequently use these data to formulate and validate a model that characterizes total leaf conductance. Conductance data were collected for two soybean genotypes, Haskell and N01, grown in a controlled water stress field during 2008 and 2009 in North Carolina. An empirical model of leaf conductance based on plant age and soil moisture content was developed. As a function of plant age, conductance was well represented by a parabolic function increasing throughout the vegetative period, peaking at approximately the time of first flower, and decreasing throughout the reproductive period through senescence. A sigmoidal function explains the relation of soil moisture content to conductance. Conductance is lower under water stressed conditions and increases to a plateau as conditions are increasingly well-watered. This new empirical model effectively quantifies the response of total leaf conductance to soil moisture and plant age. It also relates soil moisture deficit to conductance via a functional form similar to the ABA-related mechanistic Tardieu-Davies model; however, soil moisture is a more easily accessible model input.