Although the available scientific data that low-frequency magnetic fields play a role in the etiology of cancer are inconclusive, this link has been suggested by epidemiologic data and proliferated in the nonscientific literature. Electric power lines, cellular phones, and personal computers are examples of sources that have been blamed for medical problems, particularly cancer. Since exposure to low-frequency magnetic fields is universal and practically unavoidable, what can physicians advise their patients? In light of the controversy surrounding this issue, the best advice may be to minimize such exposure. Future research on the health implications of low-frequency magnetic fields appears to be warranted.