C2 ceramide is a cell-permeable analog of naturally occurring ceramides. It mediates many diverse biological activities, as do natural ceramides. These processes include differentiation of HL-60 cells,1 induction of apoptosis,2 activation of protein phosphatase 2A,3 and inhibition of the mitochondrial respiratory chain.⁴ C2 ceramide also enhances the expression of COX-2 in human dermal fibroblasts5 and stimulates the growth of bovine aortic smooth muscle cells.⁶ The ability of C2 ceramide to destabilize membranes may be responsible for its inhibition of platelet aggregation.⁷