The convection induced by turbulent buoyant plumes in a rectangular filling box (Baines and Turner, 1969) is extended to situations where the lower depths of the box are divided into two basins by a vertical barrier. The barrier restricts horizontal spreading and allows the interbasin exchange of water to occur only in the common region above the barrier height. One- and two-plume systems are considered; in the two-plume case, it is assumed that each of the plumes arises from an independent buoyancy source above each basin. The resulting two-basin circulation is characterized by different stratifications in each basin and by an overflow from one basin into the other. The spreading depths of the plumes and ambient stratification depend on the barrier height, relative basin sizes, and, in the two-plume case, the relative strengths of the two buoyancy-fluxes. These results may be of relevance to multibasin seas and oceans where the circulation produced by near-surface sources of intermediate and deep water is influenced by underwater ridges. ¿ 2001 American Geophysical Union