Methods are presented for estimating peak-flow magnitudes of selected frequencies for drainage basins in Maryland. The methods were developed by generalized least-squares regression techniques using data from 219 streamflow-gaging stations in and near Maryland, and apply to peak flows with recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years. The State is divided into five hydrologic regions: the Appalachian Plateaus and Allegheny Ridges region, the Blue Ridge and Great Valley region, the Piedmont region, the Western Coastal Plain region, and the Eastern Coastal Plain region. Sets of equations for calculating peak discharges based on physical basin characteristics and their associated standard errors of prediction are provided for each of the five hydrologic regions. Basin characteristics and flood-frequency characteristics are tabulated for 236 streamflow- gaging stations in Maryland and surrounding States. Methods of estimating peak flows at sites in Maryland for ungaged and gaged sites are presented.