This study systematically evaluates the use of proton nuclear magnetic resonance (H-1 NMR) spectroscopy for determining the composition of soybean oil ethyl transesterification product mixtures by comparing the compositions measured by H-1 NMR spectroscopy and high-performance liquid chromatography (HPLC). The influence of the sample composition on the results is also discussed. For many of the samples, the triacylglycerol (TAG), diacylglycerol (DAG), monoacylglycerol (MAG), and fatty acid ethyl ester (FAEE) contents could be determined by HPLC. When the conversion of the TAGs into FAEEs is incomplete, the evaluation of the FAEE content by H-1 NMR spectroscopy must be performed with caution because of overlapping signals in the spectrum. In this study, three equations were used to calculate the ethyl ester content from the H-1 NMR results. The contents calculated using eq 3 agree with the HPLC results the best, as shown by the slope obtained by linear regression of the two data sets.