In this paper, the STUK group examined the effects of 1800 MHz GSM mobile phone signals on the proteome of the human endothelial cell line EA.hy926. The IT'IS Foundation provided the exposure system and maintained the quality of the exposure. The results suggest that the 900GSM and 1800GSM exposures might affect the expression of some proteins in the EA.hy926 cell line. The observed discrepancy here between the expression changes of GRP78 detected with 1DE and 2DE confirms the importance of validation of the results obtained with 2DE using other methods, e.g. western blot.