Since their discovery over 100 years ago, sphingolipids have caught the eyes and the imagination of scientists. Modern science has made many new insights on the cell biology and day-to-day functions of many integral sphingolipids, especially those of ceramide. Ceramide is recognized as a vital second messenger in the signal transduction process mediated by receptors of many cytokines and growth factors. A great part of our current understanding of ceramide has been achieved from apoptosis-related studies, however recent data in the fields of immunology, endocrinology and neurobiology, also suggest a fundamental involvement of ceramide in the onset of diseases. Therefore, understanding the biology of ceramide could be a key to unraveling many biological mechanisms and provide information for the treatment of some common diseases.