Phosphatidylcholine (PC) metabolism in bovine adrenal chromaffin cells has been studied in vivo with 100 MHz 13C NMR spectroscopy. The incorporation of 13[CH3]choline was examined in cells embedded in 1% agarose strands and perfused at 37 °C. The pattern of 13C NMR spectroscopy. The incorporation of [13CH3]choline incorporation into PC of suspension cultures of chromaffin cells. The chemical shifts of labelled carbons in [13CH3]choline before and after their incorporation into PC are identical (ca 56.4 ppm). Incorporated [13CH3]choline can be released from the cells by phospholipase D which reduces the cellular PC signal by >85%, indicating that a major fraction of the labelled PC is on the external membrane surface. This application of NMR spectroscopy provides a basis for direct measurement of the in vivo metabolism of PC in functioning adrenal chromaffin cells Copyright © 1991 John Wiley & Sons, Ltd.