Field and laboratory studies were conducted to establish the water pollution potential of the improper landfill disposal of demolition waste. Water samples were analyzed from four different demolition waste sites. The results showed significant increases in hardness, alkalinity, conductivity, COD, iron, and manganese. From these field studies, the most extreme concentrations determined were 40 mg/l of iron, 9.0 mg/l of manganese, EDTA hardness of 1100 mg/l (CaCO3), and a COD of 270 mg/l. The interim results of the laboratory study, simulating unsaturated flow through demolition waste, are in close agreement with the field measurements. These results indicate the potential for subsequent deleterious environmental effects.