In the Perspective "Too many rodent carcinogens: Mitogenesis increases mutagenesis" by Bruce N. Ames and Lois Swirsky Gold (31 Aug., p. 970), the last paragraph on page 970 (continuing on page 971) was incorrectly printed. It should have read, "One major group of natural chemicals in the human diet are the chemicals that plants produce to defend themselves, the natural pesticides (4). We calculate that 99.9% (by weight) of the pesticides in our diet are natural. Few natural pesticides have been tested in at least one rodent species, and again about half (27/52) are rodent carcinogens. These 27 occur commonly in plant foods (10). The human diet contains thousands of natural pesticides, and we estimate that the average intake is about 1500 mg per person per day (4). This compares to a total of 0.09 mg per person per day of residues of about 100 synthetic pesticides (4). In addition, of the mold toxins tested at the MTD (induding aflatoxin), 11 out of 16 are rodent carcinogens." Also, in paragraph 3 on page 970, "47,000 8-hydroxydeoxyguanosines per cell" should have been "90,000" per cell.