THE B cells within the germinal centres of lymphoid organs undergo affinity maturation of their antigen receptors, a critical event for antibody memory(1-3). Follicular dendritic cells within the germinal centres retain immune complexes(4-6) that select the developing B cells for which they have a higher affinity(7). We have now identified a subset of CD4(+)CD11c(+)CD3(-) dendritic cells in the germinal centres. These are strong antigen-presenting cells for T cells, but do not co-stimulate CD40-activated B cells, These dendritic cells probably stimulate germinal centre T cells and aid the complicated processes that are required for the generation of memory B cells.