AIM: To identify the molecular basis of the endothelial target for acetylcholine (ETA). METHODS: Proteomic methods were used to monitor changes in protein expression in the first 10 h following the stimulation of human coronary endothelial cells with carbachol 100 μmol/L. Thirty proteins showing the largest changes were identified by mass spectrometry. RESULTS: Based on analysis with Image Master 2-D Elite software, about 623 protein spots were detected in control cells and 825 protein spots in carbachol-treated cells, the matching rate was 68.1%.Among all the detected spots, 39 were up-regulated and 29 were down-regulated, showing detectable changes varied from 1.7-3.8 folds. Forty one spots in the peptide mass fingerprints were successfully obtained. The most interesting feature was that all the four newly synthesized proteins belonged to the heat shock protein family.CONCLUSION: These identified proteins played key roles in the molecular mechanism of ETA.