To address the question of a possible effect of magnetic fields (MF) at 50 Hz on living systems, gene expression analyses were performed on human primary vascular endothelial cells exposed to MF of various intensities compared to control cells. Exposure protocols included continuous exposure at a single intensity (10 and 700 μT), intermittent exposure at a single intensity (700 μT), and continuous exposure to a variable-intensity field (10–30 μT). The transcriptional response of the cells was investigated using oligonucleotide microarrays containing up to 30 000 unique features. Although in individual experiments genes were identified where the expression appeared to be affected by exposure to MF, none of these genes were regulated in the same manner in subsequent repetition experiments. This is the first report of a transcriptome-wide analysis of the effects of MF exposure on human cells. The lack of a reproducible effect of MF on the expression of any genes in our investigation adds further weight to the evidence that 50-Hz MF are not capable of interacting with biological systems and thus do not represent an endothelial stress factor.