A method for primary cell culture of fetal rat gastric fundic epithelial cells was developed. The tissue was incubated with 0.125% trypsin at 4 degrees C for 8-10 hours. The epithelial cells isolated were then cultured in DMEM/F12 medium supplemented with 20% fetal calf serum. Within 24 hours the cells attached to the culture plate and became confluent in 3 days. On phase contrast microscopy, over 90% of cell possessed epithelial characteristics. Immunocytochemical studies showed: (a) 90% of cells were positive in anti-cytokeratin antibody staining; (b) 90% of the epithelial cells contained PAS positive granules; (c) 20% of epithelial cells gave a strong reaction for succinic dehydrogenase activity. Electron microscopy (EM) showed microvilli on the surface of cells, junctional complexes (tight juntion and desmosome), glycogen and mitochondria. Autoradiographic studies showed that these cells possessed the capability to synthesize DNA and this ability was maximum on day 2. This in vitro system may provide a valuable model for studies of cellular functions of gastric mucosa.