This product is a high purity, non-natural L- erythro ceramide that is ideal as a standard and for biological studies. D-erythro ceramide is the natural ceramide isomer and is involved in many biological processes including induction of cell maturation, cell cycle arrest, terminal cell differentiation, cell senescence, and cell death.1 Natural sphingosine induces dephosphorylation of retinoblastoma gene product and inhibits cell growth while L-erythro-sphingosine is 5-8-fold less active. However, the Lerythro- sphingosine is taken up by cells to the same extent as the natural sphingosine indicating that cellular uptake was not the factor influencing activity.2 Both the natural D-erythro and the non-natural L-erythro and the D- and L-threo ceramides display similar effectiveness in inducing apoptotic damage in cells.3 The protein phosphatases PP1 and PP2A, which are involved in regulating apoptosis and cell growth, are activated by D-erythro ceramide but inhibited by L-threo, D-threo, and L-erythro ceramide.4 Both D-erythro and D-threo C2 ceramides have been found to be potent inducers of IL-6 production, while neither the L-threo or L-erythro stereoisomers of ceramide were effective.5 D- and L-erythro ceramide and D- and Lthreo ceramide are also comparably effective inhibitors of protein kinase C.6