In 1988–1991 striped bass Morone saxatilis were collected for tagging from various spawning areas within the Hudson River (New York) and the Chesapeake Bay (Maryland). The fish were tagged and released during traditional periods of spawning and recovered by commercial and recreational fishermen. The proportion of fish that migrated in spring–fall from spawning areas in Chesapeake Bay to more northern waters of mid-Atlantic and New England states was estimated from the geographically stratified tag returns. Most of the tagged fish were 40–100 cm total length (TL). The estimated proportion of migrant striped bass increased with body size, and nearly all fish larger than 100 cm TL left the bay during the spring–fall migration. Sex-specific differences in migration appear to be associated with the differences in body size of mature males and females, thus lending support to previously hypothesized patterns of striped bass migration.