Retinoblastoma (Rb) is the most common malignant cancer of eye. So-Rb50 is the first Rb cell line established in China in 1988. It has passed to the 387th passage now. We collected cells of the 327th passage of SO-Rb50, purified its genomic DNA and detected it with Rb and c-myc cDNA probes respectively (normal human white blood cells DNA was the control). We found the Rb gene was deleted while c-myc gene was amplified three times. This provides a basis for further study of the regulation of tumor development and tumor reversal with this cell line in vitro.