A procedure of differential display reverse transcription polymerase chain reaction (DDRT-PCR) applicable for silver staining was optimized by adjusting the amount of several critical reagents, including total RNA, anchor primer, arbitrary primer, cDNA and dNTP. The PCR amplification products were separated on 6% vertical denaturing polyacrylamide gels. Numerous and distinct bands could be detected by silver staining. The minimum number of bands in one lane was 40, the maximum was 80 and the average was 60. The range of displayed PCR products extended from about 100 base to about 900 base. The sensitivity was 5 pg/mm². This procedure was simple, time-saving, high sensitivity and reproducible. Based on the improved procedure, the differential gene expression were studied between immature siliques of Arabidopsis wide-type and ast mutant. From nearly 16 000 cDNA fragments analyzed, 28 differential cDNA fragments were screened. After the second PCR amplification, 13 differential cDNA fragments were identified among which 7 fragments were wild type specific and 6 fragments were ast mutant specific.