Two liverwort and three moss aquatic species from different regions of the former USSR were analysed for their fatty acid composition of total lipids and triacylglycerols (TAG). Diacylglyceryltrimethylhomoserine (DGTS) and phospholipid composition were also examined. The major polar lipids found were DGTS (20.4-39.6%), PC (18.2-25.5%), PG (13.9-25.8%) and PE (9.5-19.6%). Fatty acids were analyzed by GC-mass spectrometry in total lipid extracts and in TAG. Acetylenic fatty acids in TAG varied from 6.6% in the moss, Calliergon cordifolium, to 80.2% in the liverwort, Riccia antipyretica. Three acetylenic acids were identified among the monoenoics (6a-18:1 9a-18:1 and 12a-18: 1) and dienoics (6a, 9c-18:2, 9a, 12c-18:2 and 9c, 12a-18:2). Four acetylenic acids were identified amongst the polyenoics 6a, 9c, 12c-18:3, 8a, 11c, 14c-20:3, 6a, 9c, 12c, 15c-18:4 and 5a, 8c, 11c, 14c-20:4.