The brain is rich in two LCP, docosahexaenoic acid (DHA) and arachidonic acid (AA). Small amounts of LCP are present in human milk, but not in most formulas. Studies of the effects of infant feeding regimens on visual and cognitive development in term infants have provided inconsistent results and few extend beyond 1 yr. Objective: This study evaluated development of children at age 3.25 yrs fed infant formulas with or without LCP through the first yr. Design: Infants 2 days of age were randomized to a control (no LCP), an AA+DHA (0.43 wt% AA and 0.12% DHA both from egg yolk phospholipid) or a DHA (0.20% DHA from a low-EPA fish oil) formula; breast fed infants served as a reference group. No differences in growth or development were found in the first yr and the DHA group at 14 mos had lower vocabulary scores (Pediatr Res 1997;41:1-10 & 1995;37:310A). Preplanned regression analyses controlled for birthweight, gender, ethnicity, maternal education, maternal age, child's exact age at testing, and site. Results: 157 of 196 (80%) eligible subjects were tested. There were no effects of LCP supplementation on test results in the 107 formula fed children. Stanford Binet IQ scores for the control, AA+DHA and DHA groups were(mean±SD) 103±15, 101±12, and 100±12, respectively. Scores for the Peabody Picture Vocabulary Test-Revised were 97±14, 97±16 and 96±13; mean length of utterance(morphemes) was 3.6±0.9, 3.7±0.9, 3.9±0.8. The breast fed group had higher scores in some comparisons. Conclusion: We found no evidence of effects of LCP supplementation in the first yr on cognitive function and language development at 3.25 yrs. We speculate that positive effects of supplementation reported in previous studies relate to the composition of the control formula (e.g., marginal levels of the DHA precursor, linolenic acid).Funded by Ross Products Division.