Here we describe a device for testing possible influences of high magn
etic fields on biological processes, by which alternating-current magn
etic stimuli as high as 1.7T can be administered. Experiments with a s
imple multicellular organism, the nematode Caenorhabditis elegans, rev
ealed that intermittent exposure to the magnetic fields modestly inhib
ited the animal's reproduction as well as its post-embryonic developme
nt, and caused a marked but transient derangement in its locomotory be
havior. Available evidence indicates that alternating high magnetic fi
elds can elicit both chronic and acute biological effects, but that th
e effects may be well tolerated or compensated for by the living organ
ism.