The establishment and partial characterization of a continuous cell line from the dorsal fin of red sea bream, Pagrus major, are described. The cell line, designated RSBF-2, has been subcultured for more than 100 passages since its initiation in November 2000. It was optimally maintained at 28 degrees C in Leibovitz L-15 medium with 10% foetal bovine serum. Propagation of RSBF-2 cells was serum dependent and exhibited low plating efficiency (<1.7%). Aside from long-term cryopreservation, the cells could also be kept at 4 degrees C for 72 days. The distribution of the chromosome number was 38-98 with a mode of 48. The RSBF-2 cell line was susceptible to red sea bream iridovirus but only produced a few rounded and refractory cells. Virus-inoculated RSBF-2 cells were then subcultured to generate a persistently infected cell line. RSBF-2 was also very sensitive to the extracellular products of Photobacterium damselae ssp. piscicida and produced significant fluorescent signals after transfection with pEGFP-C3. Analysis of mitochondrial cytochrome b gene sequences revealed 99% identity between the cell line and Pagrus major.