omega-3 fatty acids have recently been placed into the center of interest because of their different effects on fatty acid metabolism as well as on blood coagulation. We do not know if omega-3 fatty acids are essential during childhood, because it was seen that they may have positive effects on the development of the brains of rats and are also present in breast milk. The following report presents the recent state of the scientific knowledge. In fish and grain oil one can find not only omega-6 fatty acids as e.g. arachidonic acid (AA: C 20: 4 omega-6), but also omega-3 fatty acids (e.g.: linolenic acid: C 18:3 omega-3). They are always in a specific ratio to the other: If there are higher concentrations of omega-3 fatty acids, one can find less amounts of omega-6 fatty acids, and vice versa. The most important representatives of the omega-3 fatty acids are metabolites of linolenic acid, such as docosahexaenoic acid: C 22: 6 omega-3 (DHA) and eicosapentaenoic acid: C 20: 5 omega-3 (EPA). The beneficial influence, especially of DHA, on the postnatal development of the retina and brain has been demonstrated in rats and rhesus monkeys. It could be shown that the fatty acid composition of phospholipids of red blood cells conforms to that of the CNS. Nearly the same values could be achieved in infants with both, a diet enriched with fish oil and a feeding with breast milk; this seems to be essential especially for preterm infants, who always have a DHA-deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)