Sphingolipid metabolites are important regulators of cell growth and death. In the present study, we examined the function of cell surface sialic acid in exogenous sphingosine-l-phosphate (S-l-P) or sphingosine-induced cell death. HBL-2 human diffuse large B cell lymphoma cells were incubated with or without Vibrio Cholerae neuraminidase followed by S-l-P or sphingosine. Flow cytometric analysis using Limax flavus agglutinin, a sialic acid-specific lectin, showed that sialylated glycoconjugates are present on the surface of HBL-2 cells and that they were removed by neuraminidase. In addition, the pretreatment with neuraminidase enhanced S-l-P- and sphingosine-induced cell death, an effect that was not dependent on caspase activation. Furthermore, the cell death induced by S-l-P and sphingosine was morphologically distinct from apoptosis. We further examined S-l-P-induced cell death in two clones of HBL-8 Burkitt lymphoma cells with different amounts of cell surface sialic acid. Clone 3G3, which is hypersialylated, was less sensitive to S-l-P than the 3D2 clone, which is hyposialylated, suggesting that the extent of surface sialylation influences the sensitivity to S-l-P. In conclusion, S-l-P and sphingosine induce cell death, and the sensitivity of human B lymphoma cells to these agents appears to depend on the amount of sialic acid on their cell surfaces.