Preliminary determinations of the magnitude and frequency of peak flows resulting from the storms of December 1996 and January 1997 were made at 292 streamflow gaging stations located in 45 counties in northern and central California. Peak flows were the largest on record at 106 stations, and recurrence intervals were greater than 100 years at 32 stations. Two separate frequencies were determined for the 1997 peak flow at each streamflow station: a frequency based on an analysis that includes annual peak flows through the 1996 water year (ending September 30, 1996) and a frequency based on an analysis that includes the 1997 peak.