The systemic absorption from topical applications of 40% zinc oxide ointment was investigated in a series of healthy subjects (phase one) and in patients receiving total parenteral nutrition (phase two). In the first phase, six subjects completed a controlled, cross-over trial involving 3 hourly serum sample determinations for zinc concentration following a massive application of 40% zinc oxide ointment and plain petrolatum ointment. There was a mean increase in serum zinc from 107.3 +/- 5.32 to 116.1 +/- 5.02 micrograms/dL 1 hr after application of 40% zinc oxide ointment (p greater than 0.05). Three patients receiving total parenteral nutrition completed phase two of the protocol in which 40% zinc oxide ointment was applied daily to a specified area of the thigh. Analysis of these patients' serum revealed that the zinc concentrations remained relatively constant over the 10-day study period. These findings suggest that topical applications of 40% zinc oxide ointment do not result in significant absorption. This study serves as a starting point for further investigations.