The B-cell antigen receptor acts during B-cell activation both to initiate signalling cascades and to transport antigen into the cell for subsequent processing and presentation. Recent evidence indicates that membrane microdomains, termed lipid rafts, have a role in B-cell activation as platforms for B-cell receptor (BCR) signalling and might also act in antigen trafficking. Lipid rafts might facilitate the regulation of the BCR during B-cell development by B-cell co-receptors, and during viral infection. So, lipid rafts seem to be an important new piece of the B-cell signalling puzzle.