The relationship between dexamethasone-dependent changes in intracellular sphingosine levels, energy and phospholipid metabolism have been investigated by 31P-NMR spectroscopy and high-performance liquid chromatography. The cellular functions have been evaluated by cellular growth and immunoglobulin M secretion (IgM). Significant increases in intracellular phosphorylcholine (PCho), extracellular choline (Cho), and endogenous sphingosine levels were observed only at 30 min incubation with dexamethasone. These results confirmed a sphingosine-dependent hydrolysis of choline-linked phospholipids (Miccheli, A., Ricciolini, R., Piccolella, E., Delfini, M. and Conti, F. (1991) Biochim. Biophys. Acta 1093, 29-35). Furthermore, no significant variations were evidenced at hours 1, 2, 6 and 18 of incubation. Dexamethasone causes an inhibition of cellular growth and IgM secretion as well as the sphingosine treatment. The results suggest that the effect of dexamethasone may be mediated by endogenous sphingosine production in Epstein-Barr virus transformed B lymphocytes.