The synthesis by a modified malonic ester procedure of C2-elongated polyunsaturated fatty acids from their natural precursors was described. Using the suggested Scheme 1, (7Z,11Z,14Z)-7,11,14-eicosatrienoic, (8Z,11Z,14Z,17Z)-8,11,14,17-eicosatetraenoic, (5Z,8Z,11Z,14Z,17Z)-5,8,11,14,17-eicosapentaenoic, (8Z,11Z,14Z,17Z)-8,11,14,17-docosatetraenoic, (7Z,10Z,13Z,16Z,19Z)-7,10,13,16,19-docosapentaenoic, and (6Z,9Z,12Z,15Z,18Z,21Z)-6,9,12,15,18,21-tetracosahexaenoic acids were synthesized. Their structures were confirmed by GC, UV, and MS data, which coincided with those of natural compounds. The target compounds were shown to be free from by-products, which could result from Z-E isomerization or migration of double bonds. The overall yields of the four-step synthesis of C2-elongated polyenoic acids were 25-30%. © 1996 MAEe cyrillic signK Hayκa/Interperiodica Publishing.