A hydrologic study of Butternut Creek, near Jamesville, Onondaga County, N.Y., was done to develop inflow and outflow hydrographs of the ' probable maximum flood ' and the ' standard project flood ' of Jamesville Reservoir, as defined by the U.S. Army Corps of Engineers. The inflow and outflow discharges of the probable maximum flood were computed to be 23,600 and 23,100 cubic feet per second, respectively, and of the standard project flood, 9,400 and 8,800 cubic feet per second, respectively. A rating curve computed for the dam spillway indicates that water-surface elevations produced at the dam by runoff from both the standard project flood and the maximum probable flood would be above the top of the spillway abutments. The 10- and 100-year peak discharges at the Butternut Creek gaging station were computed by the HEC-1 program of the Corps of Engineers to be 2 ,160 and 3,450 cubic feet, respectively, as compared to 1,680 and 2,810 cubic feet per second computed by a log-Pearson type III analysis of the station data. The HEC-1 values are within the 5- and 95-percent confidence limits of the log-Pearson type III values. (Kosco-USGS)