Recent advances in genomics and proteomics, combined with the facilitated generation and analysis of transgenic and gene-knockout animals, have revealed new complexities in classical biological systems, including the B-cell compartment. Studies on an 'old', but poorly characterized, B-cell subset — the naive, marginal-zone (MZ) B-cell subset — over the past two years have spawned an avalanche of data that encompass the generation and function of these cells. Now that the initial 'infatuation' is over, it is time to reconsider these data and generate some conclusions that can be incorporated into a working model of the B-cell system.