An interdisciplinary study has been undertaken in Redwood National Park, Calif., to describe parts of the ecosystems and recent changes in the intensity of erosion and sedimentation, define processes that may alter the natural ecosystems, and assess the impact of recent road construction and timber harvest. This report is the second of a series that will present data collected in this study. Stream-discharge and water-quality data were collected at 53 sampling stations in the Redwood Creek and Mill Creek drainage basins. Measurements included the following variables: Stream stage and discharge; turbidity; sediment; onsite water-quality determinations of temperature, pH , total alkalinity, specific conductance, and dissolved-oxxygen concentration; chemical analyses of water samples for major dissolved solids, selected trace elements, nitrogen, phosphorus, and organic carbon; chemical analyses of bottom sediment for organic carbon and pesticides; bacteria; benthic invertebrates; fish; periphyton; phytoplankton; and seston. Additional data include changes in geometry at 10 stream-channel cross sections along Mill Creek and the distribution of erosional landforms in the Mill Creek drainage basin; quantity and chemical composition of rainwater; and the intragravel-streambed condition at selected stations in the Redwood Creek drainage basin. (Woodard-USGS)