After years of weighing in on issues like secondhand tobacco smoke and radon exposure, Jonathan Samet, MD, is accustomed to controversy. And last week, Samet, a University of Southern California physician and epidemiologist, found himself at the center of debate again as chairman of a World Health Organization committee ruling on the health effects of cellphone use. The International Agency for Research on Cancer, which consisted of 31 scientists from 14 countries, concluded that cellphones are "possibly carcinogenic," putting the devices in the same category as about 260 chemicals, pesticides and other substances, including coffee, that might lead to certain cancers. The finding, which is the first time a major health organization has concluded there is a possible risk to cellphone use, drew an immediate rebuke from the cellphone industry. It also put Samet, who has a presidential appointment to the National Cancer Institute's advisory board, at odds with two of the country's top cancer groups. The American Cancer Society said the findings were based on flawed data and should be interpreted with "great care." More surprising is the fact that a representative from the National Cancer Institute skipped the vote. The institute says the committee member will join dissenters in writing a minority opinion.