The four isomers of 2,3,5‐trimethylmorpholine and those of 2,3,6‐trimethylmorpholine have been synthesized from appropriately substituted ethanolamines and separated by means of preparative gas‐liquid chromatography. The configuration of each isomer was determined from 270 MHz FT‐nmr studies of the magnitudes of the methine‐methine and methine‐methylene proton coupling constants. The evaluated chemical shifts of axial methyl groups are discussed.