High spatial resolution current and hydrographic measurements have been made across a tidal intrusion front in the James River estuary, Virginia, during the first few hours of flood. The current measurements were made with a surface-towed acoustic Doppler current profiler which was used in both profile and side-scan configurations. The profile data show a 30--50 cm s-1 inflow of water from the Chesapeake Bay, a time-evolving across-front density gradient, and downward velocity beneath the front of about 15 cm s-1. The side-scan observations directly measure the across-front change in current and provide a view of the three-dimensional character of the frontal interface. The near-surface horizontal strain rate, a critical parameter for understanding the modulation of surface waves across the front, is estimated to be about 0.04 s-1. Using Phillips' <1984> theory as a guide, fronts with such large strain rates as these should be discernible in imagery from the ERS 1 C band synthetic aperture radar for wind speeds of ≤4 m s-1.