A series of hydroxy fatty acids was identified from a polar glyceride milk-fat fraction. These acids were identified as trimethylsilyl (TMS) ether methyl ester derivatives. Identification was achieved by mass spectral analysis and comparison of gas chromatographic retention times with authentic compounds. Mass spectral fragmentation patterns of the TMS ether methyl esters were obtained, and correlation of important ions for structural identifications were made. In addition, semiquantitative data are presented.