The aim of this study was to investigate the molecular mechanisms underlying the antitumour effects of CD40L through analysing the change of genes expression profile in AGS using Affymetrix Gene Chip. Human gastric carcinoma AGS cells were first incubated with 2 μg/ml sCD40L or equal volume of medium (control) in F12 medium. RNA was isolated from AGS and were reverse transcribed, labeled with digoxigenin-11-dUTP, and then hybridized with Clontech Atlas mouse cDNA expression arrays for comparison. Performing clustering analysis, we found that 7 detected genes were down-regulated and 38 were upregulated as the sCD40L acted on AGS. To further verify the results of gene chip screening, Gene Database was searched, finding that the most significantly up-regulated genes were Gadd45a, c-Jun and Bcl-2, and the most significantly down-regulated genes were Cyclin D1, CDC6, TNFR10B, c-IAP2 and ORC5L. Based upon these findings, the signalling pathways that possibly mediate CD40-induced apoptosis are proposed.