Some effects of extremely low frequency electromagnetic fields (ELF‐EMFs) on human spermatozoa are reported. Significant increases in the values of the motility and of the other kinematic parameters have been observed when spermatozoa were exposed to an ELF‐EMF with a square waveform of 5 mT amplitude and frequency of 50 Hz. By contrast, a 5 mT sine wave (50 Hz) and a 2.5 mT square wave (50 Hz) exposure did not produce any significant effect on sperm motility. The effects induced by ELF‐EMF (50 Hz; 5 mT) during the first 3 h of exposure persisted for 21 h after the end of the treatment. These results indicate that ELF‐EMF exposure can improve spermatozoa motility and that this effect depends on the field characteristics. Bioelectromagnetics. © 2006 Wiley‐Liss, Inc.