Immature B cells undergo key maturation and selection events after migrating to peripheral lymphoid organs. We will review recent advances in our understanding of the cell populations and molecular interactions underlying the differentiation of immature peripheral B cells into mature marginal zone (MZ) and follicular B cells, and discuss potential mechanisms by which numbers of MZ and follicular B cells are maintained. We will also discuss current controversies over the identity of precursor cells for MZ and follicular B cells, and propose a potentially unifying model for precursor-product relationships in peripheral B cell maturation.