The low DHA content of the milk of women in the United States has led some to suggest DHA supplementation of breastfeeding women. However, data concerning the efficacy of supplementation are lacking. To provide such data, we have determined the effects of DHA supplementation of lactating women on the visual function and growth of the recipient infants. Mothers were assigned randomly and blindly to receive either ≈200 mg of DHA daily (Group 1; n=36) or placebo (Group 2; n=19) for 120 days after delivery. The fatty acid pattern of maternal milk and infant plasma phospholipid (PL) was determined 120 days post-delivery. Visual function of infants was assessed at 120 and 240 days of age by transient visual evoked potential (VEP) latency and amplitude; visual acuity was measured at the same times by sweep VEP and the Teller Acuity Card Procedure. Growth was monitored throughout the study. At 120 days, milk total lipid DHA content of Group 1 was twice that of Group 2 (0.4 vs. 0.17 mol% of total fatty acids, p<0.001); infant plasma PL DHA content was 45% higher (p<0.001) and arachidonic acid, C22:4n-6 and C22:5n-6 contents were 9, 34 and 39% lower (p=0.04, <0.001 and <0.001). There were no differences between groups in VEP latency (126 ± 11 vs. 122± 13 and 115 ± 10 vs. 115 ± 9 msec in Group 1vs. Group 2 at 120 and 240 days, respectively), VEP amplitudes (32.6± 13 vs. 32.3 ± 13 and 23.3 ± 12.5vs. 30.6 ± 13 μvolts), sweep VEP acuity (8.3 ± 1.8vs. 8.5 ± 1.6 and 8.7 ± 1.8 vs. 8.3 ± 1.3 cyc/deg) or Teller Card acuity (5.4 ± 2.4 vs. 6.0± 3.0 and 11.4 ± 4.6 vs. 13.1 ± 7.5 cyc/deg) at either age. No measure of visual function correlated significantly with either milk DHA or infant plasma PL DHA content at 120 days of age. There were no statistically significant differences in weight, length, head circumference or skinfold thicknesses between groups at either 120 or 240 days of age. These data show that maternal DHA supplementation increases the DHA content of maternal milk as well as the plasma PL DHA content of the recipient infant but confers no detectable benefits with respect to visual function.