Radioisotopic analyses for carnitine content were done on infant formula, formulas for tube feeding, food supplements, and chemically defined diets. The carnitine content of the diets depend on the protein source. Products whose main protein source is soy protein isolate, casein, or egg white solids contain 4 nmole carnitine per milliliter or less, with most of them containing undetectable amounts of carnitine. Products based on milk or beef contain 50 to 656 nmole carnitine per milliliter. The daily requirement of the body for carnitine is unknown. Evidence is discussed that indicates that the possible use of carnitine as a supplement to formula diets intended for long-term care needs to be considered.