C-8 ceramide is a cell-permeable analog of naturally occurring ceramides. Unlike C-2 ceramide, it is metabolized within cells to generate natural ceramides, often causing a dramatic increase in cellular ceramide levels. For this reason, treatment of cells with C-8 ceramide may more closely mimic the effects of ceramide elevation than does treatment with shorter chain ceramide analogs. C-8 ceramide likely mediates many diverse biological activities, as do natural ceramides. It promotes the differentiation of human keratinocytes and induces apoptosis of both human leukemia cells and the U937 cell line.