This study was carried out in metabolically stable infants aged from one to six months receiving artificial food. The lipid serum fraction presenting changes characteristic of essential fatty acid (EFA) deficiency was determined. A preliminary study (n = 13 samples) showed that analysis of total fatty acids (TFA) and of phospholipids (PL) was more discriminatory than analysis of free fatty acids (FFA), triglycerides (TG) or esterified cholesterol (EC). Comparison of TFA and PL (n = 25 samples) confirmed literature data; in particular, C18: 2 n-6 and C20: 4 n-6 decreased whereas C20: 3 n-9 increased. These changes were clearer and significantly greater (p less than 0.001) for C20: 3 n-9 and C20: 4 n-6 of the PL, but were also very significant for the TFA compared to healthy controls. The C20: n-9/C20: n-6 ratio was identical for all fractions. TFA analysis by gas-liquid chromatography is faster and less costly than analysis of lipid fractions and provides sufficient data for screening of EFA deficiency.