There are about 100 000 different genes in higher organisms, and only 15% of them are expressed in any individual cell. Thus it is very important to isolate specific genes.Comparing with substractive hybridization, differential display is a more effective approach to isolate specifically expressed genes. In differential display, reverse transcripted products of mRNA are amplified and displayed on sequencing gel. Then differentially expressed genes are isolated. Although there are many difficulties in using this method, as further improved, it will be useful in various fields.