The geology, hydrology, and distribution of contaminants in the Galena-Platteville aquifer in the vicinity of the Parson?s Casket Hardware Superfund site in northeastern Belvidere, Ill., were characterized on the basis of data collected from boreholes using geophysical logging and packer assemblies. Horizontal flow in the Galena- Platteville aquifer is affected by a network of subhorizontal fractures that are concentrated in the weathered part of the bedrock, vugs and fractures present from the bottom of the weathered bedrock to the top of a shaley layer at about 662 ft (feet) above sea level, and through a widespread subhorizontal fracture at about 524 ft. Inclined fractures provide pathways for vertical flow within the Galena-Platteville aquifer. Some fractures and flow pathways appear to be affected by the stratigraphy of the Galena-Platteville deposits. Water-level data indicate the potential for downward flow within the Galena-Platteville aquifer. During periods when pumping in nearby municipal-supply wells is minimal or absent, the direction of flow through the fracture at about 524 ft above sea level is south toward two industrial-supply wells. Flow through the fracture is toward the municipal-supply wells when they are being pumped. Flow in the upper part of the Galena-Platteville aquifer does not appear to be affected by pumping in nearby water-supply wells. Chlorinated ethenes were the volatile organic compounds detected most often and at the highest concentration in the Galena-Platteville aquifer beneath northeastern Belvidere. Volatile organic compounds are migrating primarily to the southeast toward the Kishwaukee River, with components of movement to the north, east, and west. Volatile organic compound and monitored natural attenuation parameter data indicate reductive dechlorination of some chlorinated ethene compounds is occurring under either nitrate or iron-reducing conditions in the unconsolidated deposits and possibly the upper part of the Galena-Platteville aquifer near the center of the plume. Oxidizing conditions appear to be present at least in the upper part of the aquifer beneath most of the study area, and the occurrence of reductive dechlorination in the Galena-Platteville aquifer beneath most of the area of investigation is not clearly indicated.