Three young infants with protracted diarrhea and malnutrition were successfully treated by means of intravenous nutrition, which included infusions of fat emulsion (Intralipid) and of fresh frozen plasma. Three to five weeks after termination of intravenous feeding, and after full recovery, they developed pneumococcal septicemia and meningitis. One infant died, and postmortem examination showed diffuse deposition of “intravenous fat pigment” in hepatocytes and in reticuloendothelial cells. In the two infants who recovered, follow-up studies did not disclose any primary derangement of immunologic function. We propose that the infused fat may have caused a temporary depression of immunologic defense mechanisms, predisposing these infants to the pneumococcal infection; the delay in onset of the infection might be attributed to a short-lasting protective effect of fresh frozen plasma which was included in the intravenous feeding regimen.