Responses of the small hear shock protein gene, hsp-16, were examined in transgenic Caenor-habditis elegans exposed to electromagnetic fields. Expression of the hsp-16-lacZ gene was enhanced when transgenic animals were exposed to magnetic fields up to 0.5 T at 60 Hz. The hsp-16 promoter was more efficiently expressed at the embryonic than at the post-embryonic stage irrespective of exposure. Promoter activity was more sensitive to the stimulus in the intestine at the post-embryonic stage. Evidence is presented that the induction occurs at the transcriptional step of hsp-16. (C) 2001 Wiley-Liss, Inc.