Attempts were made to investigate on the fatty acids of Lentinus lepideus Fr. Fats were extracted from its carpophores and saponified with alcoholic potassium hydroxide. Isolated fatty acids were methylated and were subjected to column chromatography and GLC. Six saturated fatty acids, i.e., dodecanoic, tridecanoic, tetradecanoic, pentadecanoic, hexadecanoic and octadecanoic acids were identified. Especially myristic acid was abundant. Four unsaturated fatty acids, i.e., hexadecadienoic, oleic, linoleic, linolenic acids, were identified. Especially oleic and linoleic acid were abundant.