Beginning in April 1989, water quality measurements were made at six sites in or near Pamlico River estuary and at five sites in or near the Neuse River estuary. Measurements taken at 15-minute intervals included near-surface and near-bottom specific conductance; near-surface water temperature; and near-surface, mid-depth, and near-bottom dissolved-oxygen concentrations. Water-quality data obtained from continuously-monitored sites in the Pamlico River estuary and the Neuse River estuary are presented for the period April 1989 through September 1990. Instantaneous values for selected periods are summarized in a series of box plots. Instantaneous maximum and minimum values are also tabulated. Daily mean values of salinity, water temperature, and dissolved-oxygen concentrations for the entire period are presented in tables and graphs.