The 35S sulfolipids synthesized by purified cultures of rat Schwann cells, fibroblasts, and a rat cell line (RN2) were studied. Schwann cell 35S sulfolipids were almost entirely [35S]sulfatide, as shown by TLC in two different solvent systems with unlabeled authentic sulfatide run in the same track. RN2 and fibroblasts did not synthetize significant amounts of sulfatide, by the same criteria. Previous studies failed to detect any characteristic myelin components, including sulfatide, on Schwann cells after several days in culture )Brockes et al., 1980a; Mirsky et al., 1980). My results show that Schwann cells continue to synthesize some sulfatide in the absence of neurons.