A method using gas chromatography-mass spectroscopy (GC-MS) was developed to assess phenotypic differences in the fatty acid composition of 143 accessions of Perilla frutescens varieties that originated from different Chinese provinces, Japan, and Britain. Thirty-six compounds identified in the analysis included a number of saturated fatty acids and positional isomers of unsaturated fatty acids. A wide range in phenotypic variation was noted within each of five major fatty acids [16: