Recently, significant interest has developed regarding the effects of exposure of the human body to electromagnetic fields, especially related to the issue of whether or not electromagnetic fields have carcinogenic potential. In today's living environment, there are many devices that generate electromagnetic fields, such as MRI machines used in medical care, electrical power transformer stations and power lines, which generate alternating magnetic fields, electric household appliances and, in the future, linear motor cars. In addition, exposure to high-frequency electromagnetic fields has increased due to the recent growth in the use of mobile phones—more than 90 million mobile phones being used in Japan alone. Therefore, human beings are exposed to electromagnetic fields much more frequently than in the previous natural environment. Here, I review the present status of investigations regarding the effects of extremely-low-frequency (ELF) and radio-frequency (RF) electromagnetic fields on living organisms; especially on the response of cells and genes to these electromagnetic fields, including studies conducted at my institution. Animals and epidemiological studies on the effects of ELF electromagnetic fields are also reviewed. I also introduce an evaluation on carcinogenic effects of electromagnetic fields conducted by the International Agency for Research on Cancer (IARC), where I was a member of a working group and participated in the evaluation meeting at IARC.