This report presents a practical means of predicting the probable magnitude of floods on streams in New York State. Because of the limited amount of data on small drainage basins this method is not applicable to sites where the drainage area is less than 10 square miles or to streams where flood peaks are affected materially by manmade regulation. Flood data based on records collected at gaging stations having 5 or more years of record not affected by unnatural regulation or diversion were used to define two types of curves. The first is a composite frequency curve. It expresses the relationship between the mean annual flood and floods of recurrence intervals ranging from 1.1 to 50 years. The second type defines the relation of the mean annual flood to the drainage area above the site. The result obtainable from the combination of the two curves is a flood-frequency curve for any site in the State, gaged or ungaged, within the range of drainage area and recurrence interval defined by the base data.