We analyzed sister chromatid exchanges (SCE) frequencies as an indicator of DNA damage induced in human lymphocytes in vitro by a low-level pulsed electromagnetic field. We studied the effect of low-level pulsed electromagnetic fields on human chromosomes with the cytogenetic assay of sister chromatid exchange (SCE) analysis. After the human peripheral lymphocyte cultures were exposed in vitro to the electromagnetic field at different intensities, no significant differences were observed when comparing with the control group as to the number of SCE.