The ward delivery of fat-soluble vitamins in parenteral nutrition solutions was simulated in a laboratory situation. Radioactively labeled vitamins A, D, and E were used in tracer studies to follow their nonradioactive counterparts during addition to a parenteral solution and subsequent passage through a standard infusion set. Using this quick convenient method, it was possible to monitor delivery over an entire 24-hour infusion period. Average recovery for vitamins A, D, and E was 31%, 68% and 64%, respectively. From comparison of various sampling sites during the experimental period, it seems clear that the fat-soluble vitamins appear to adhere to the bag and tubing. In light of these findings, we suggest a reexamination of the method of solubilization of fat soluble vitamins and of the materials used in the manufacture of clinical infusion equipment.