As part of the first-order assessment of potential manganese nodule processing reject waste materials, the Bureau of Mines estimated the physical and chemical characteristics of reject waste materials that would be generated from each of five potential process flowsheets. These processes were chosen because of their economic and technical feasibility for first-generation nodule processing. A brief description of the five processes is given to show process inputs and outputs. The physical characteristics are predicted based on land-based laterite processing where applicable, and where no land- based analog exists, on the basis of process chemistry. The probable chemical characteristics such as element content and compound form are tabulated for each process for 16 elements: as, ba, be, cd, CO, cr, cu, fe, mn, mo, ni, pb, sb, se, tl, and zn. These elements were chosen based on their presence on the toxic substance list of priority pollutants, extraction procedure (ep) toxicity criteria, and major and minor elements of economic importance (co, fe, mn, and mo). Physical and chemical analyses as well as results of the ep toxicity test of one industrially supplied pilot plant reject waste material are presented.