We have used a time-dependent magnetohydrodynamic (MHD) simulation to investigate the magnetic topology of an idealized streamerlike configuration in three dimensions. Starting from an initially current-free multipole field and a transonic flow, a quasi-steady, streamerlike configuration forms. The simulated streamer exhibits a closed magnetic field region bounded by a current layer and surrounded by open fields. This helmet region is surrounded by a current layer, with an enhanced density in the closed field and current sheet regions. The simulated streamer has a finite longitudinal extent, with the closed field region primarily confined to the center of the structure. ¿ American Geophysical Union 1990