Rapid development, population growth, and the changes in land and water use accompanying development are placing increasing stress on water resources in the Taunton River Basin. An assessment by the Massachusetts Department of Environmental Protection determined that a number of tributary streams to the Taunton River are impaired for a variety of beneficial uses because of nutrient enrichment. Most of the impaired reaches are in the Matfield River drainage area in the vicinity of the City of Brockton. In addition to impairments of stream reaches in the basin, discharge of nutrient-rich water from the Taunton River contributes to eutrophication of Mount Hope and Narragansett Bays. To assess water quality and loading in the impaired tributary stream reaches in the basin, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection compiled existing water-quality data from previous studies for the period 1997-2006, developed and calibrated a Hydrological Simulation Program-FORTRAN (HSPF) precipitation-runoff model to simulate streamflow in areas of the basin that contain the impaired reaches for the same time period, and collected additional streamflow and water-quality data from sites on the Matfield and Taunton Rivers in 2008. A majority of the waterquality samples used in the study were collected between 1999 and 2006. Overall, the concentration, yield, and load data presented in this report represent water-quality conditions in the basin for the period 1997-2008. Water-quality data from 52 unique sites were used in the study. Most of the samples from previous studies were collected between June and September under dry weather conditions. Simulated or measured daily mean streamflow and water-quality data were used to estimate constituent yields and loads in the impaired tributary stream reaches and the main stem of the Taunton River and to develop yield-duration plots for reaches with sufficient water-quality data. Total phosphorus concentrations in the impaired-reach areas ranged from 0.0046 to 0.91 milligrams per liter (mg/L) in individual samples (number of samples (n)=331), with a median of 0.090 mg/L; total nitrogen concentrations ranged from 0.34 to 14 mg/L in individual samples (n=139), with a median of 1.35 mg/L; and total suspended solids concentrations ranged from <1 to 69 mg/L in individual samples (n=155), with a median of 5.3 mg/L. Concentrations of total phosphorus and total nitrogen in most of the samples collected from the impaired-reach areas were higher than various nutrient guidelines for reference streams in the northeast. Among the impaired reaches, median total phosphorus concentrations ranged from 0.016 mg/L in the Rumford River (impaired reach MA62-39) to 0.22 mg/L in the lower part of the Salisbury Plain River (MA62-06); median total nitrogen concentrations ranged from 0.61 mg/L in the Rumford River (MA62-39) to 6.2 mg/L in the lower Salisbury Plain River (MA62-06), and median total suspended solids concentrations ranged from 2 mg/L in the Rumfo...