B cell development culminates in the formation of plasma cells, potent secretors of the immunoglobulins (Ig), proteins crucial for the health of the organism. Two distinctive and crucial steps are required during B cell differentiation. First, variable gene segments encoding the antigen-binding region of Ig undergo directed rearrangement through a process known as V(D)J recombination. Second, alternative processing of the Ig heavy chain mRNA transcript enables plasma cells to secrete high levels of Ig protein. This review focuses on the molecular mechanisms that control V(D)J recombination in B cell progenitors and alternative RNA processing in plasma cells.