Recent advances in the identification of mouse plasma cells have enabled a more detailed assessment of their development and maintenance to be undertaken. Insertion of the gene encoding green fluorescent protein into the Blimp1 locus has allowed measurement of the efficiency and kinetics with which subsets of mature B cells generate antibody-secreting cells (ASCs) after culture with a series of mitogens, with and without co-stimulation. In vivo identification of plasma cells has allowed their phenotype to be defined and changes in their frequency as a result of aging and immunisation to be monitored. This new approach has allowed also a more precise definition of the genetic program activated in plasma cell differentiation. In this review we cover these aspects of plasma cell development with a particular emphasis on the B-cell subsets giving rise to the plasma cells and to their maintenance once formed.