The four electronic moisture meters most commonly used by Iowa grain dealers were compared with the official United States Department of Agriculture (USDA) air-oven method on 881 samples of corn from the 1979 and 1980 harvests. Samples ranged in moisture from 11% to 38%, wet basis. With the manufacturer-developed calibrations used in 1979, all four brands gave biased readings with respect to the air-oven method. Calibration bias errors differed among brands and ranged from approximately 1.5% to -3.5% moisture content. A recalibration between the 1979 and 1980 harvests reduced both this bias and the discrepancy among meter brands. Random errors originated from three sources: the electrical properties of different samples (contributing about 85% of the total random error), the repeatability of a meter test on a specific sample (contributing about 10%, and the repeatability of the oven method on a specific sample (contributing about 5%. The coefficient of variation of a meter test with respect to the oven varied with moisture content and increased from a minimum of 2.5% to 15.5% moisture corn to a maximum of 4.5% at both 11% and 38% moisture corn.