Alpha-linolenic acid deficiency (ALAD) is described in five adults receiving long-term gastric tube feeding with a commercially available powdered formula mixed with water and/or skimmed milk. Three patients receiving the same powder mixed with whole milk showed no signs of essential fatty acid deficiency (EFAD). The patients showed scaly dermatitis and skin atrophy. In four patients, supplementing with cod liver oil and soya oil for 4 weeks normalized n-3 acids in plasma and red cells, while n-6 acids remained unchanged or decreased slightly. At the same time, skin changes were normalized. In the fifth patient, supplementing with ethyl linolenate started to normalize skin changes within 5 days, and after 2 weeks had increased the red cell concentration of 22:6n-3 threefold. Simultaneously, 20:4n-6 increased twofold, to above control level. Minimal daily requirement of alpha-linolenic acid and of long-chain n-3 acids is estimated to be 0.2% to 0.4% and 0.1% to 0.2% of calories, respectively.