The infant's requirements for essential fatty acids (EFA) have been calculated by different workers from the same limited number of observations which depended on the use of butterfat, linoleic acid, and its esters as the source of EFA. The linoleic acid content of the butterfat employed was determined by a method of known not to be specific for the biologically active linoleic acid (cis cisC18:2omega6). The assay reported (3.3%) is about double that (1+01.6%) usually anticipated. If the butterfat used was actually of average linoleic acid content, then estimates of requirements are about twice the true values. In some tests, linoleic acid or its esters were used rather than fat or triglycerides. In other tests the total fat content of the diet was very low, and the tocopherol content of the diet was not controlled. All of these factors could adversely affect linoleic acid utilization and so exaggerate EFA requirements. If minimum EFA needs are as high as those suggested (1.0%) of cal), deficiency should be commoner than it in fact is. For the reasons noted above it is believed that the minimum requirements for EFA have been set far too high and are in fact less than 0.5% of cal, so that a daily allowance of 65 mg/100 cal (about 0.6% cal) should provide an ample margin of safety.