Rainfall-runoff data are presented for eight selected drainage basins in Somerset County, New Jersey, for the 1980 through 1984 water yr. In order to improve the existing methods for estimating flood-frequency and magnitude throughout the county, in their flood-monitoring efforts by providing real-time data, rainfall-runoff data were collected and a data base was created. The rainfall-runoff data were recorded at 5-min intervals and were stored in the U.S. Geological Survey, New Jersey District computer. Rainfall data were collected at two sites within each drainage basin in order to improve areal coverage and data continuity. Data from eight rainfall-runoff gaging stations and eight auxiliary rainfall gages are summarized. Rainfall and runoff data for selected storms also are summarized. (USGS)