Cement kiln dust (ckd) produced in the contiguous United States and Hawaii was characterized as part of the Bureau of Mines program in minerals environmental technology. The mineralogical and chemical composition was determined for 113 ckd samples from 102 plants that normally send ckd waste to landfill. Characterization included the determination of 28 elements, 7 anion species, carbon dioxide, noncarbonate carbon, and chemically bound water. Mercury was determined in 16 samples. Interelement correlation coefficients were determined for 23 elements, 5 anions, co2, noncarbonate carbon, and chemically bound water. To assess the hazardous waste potential of ckd, the U.S. Environmental Protection Agency extraction procedure (ep) toxicity test was performed on all 113 ckd samples. All but one sample were in compliance with the test; the noncomplying sample slightly exceeded the ep toxicity test criterion for lead.