[1- 14C]Palmitic acid was injected intraperitoneally into young rats (12–13 daysold) to study the label distribution over an extended period of 2 months during whichtime rapid growth and active myelination occurs. It was found that, 24 h after injection,brain palmitate still had 78% relative carboxyl activity. It was also noted thatlabel persisted in the carboxyl carbon of brain palmitate even after an extended periodof 2 months. Radioactivity distribution and specific activities of 18:0, 18:1, 20:4 and 22:6,conclusively showed that these fatty acids were synthesized by chain elongation.Similarly, radioactivity in the cholesterol fraction indicated that injected palmitatewas degraded to form radioactive acetate; thus it was surprising to find that radioactivityin brain palmitate was not redistributed by de novo synthesis from radioactiveacetate. Hypothetical possibilities for this finding are discussed.