The synthesis and turnover of cell surface H-2 alloantigens were studied in murine splenocytes by the anti-H-2-binding method to separate precursor-labeled surface from intracellular molecules. Results indicate that newly synthesized H-2 antigen, labeled in either its peptide or carbohydrate portion enters a relatively small pool of intracellular H-2 antigen and then is rapidly transported to the plasma membrane which represents a larger compartment. The simplest interpretation of these findings is that H-2 antigen is synthesized and transported along a conventional secretory pathway. Pulse-chase experiments indicate that H-2 antigens are not readily chased from the plasma membrane and are not shed or internalized during short-term culture. The aforementioned observations are discussed in terms of a cellular heterogeneity.