A diverse antibody repertoire is essential for an effective immune response.In the past, the vast repertoire size (estimated at 109) has prevented significant diversity and usage characterization.Only recently, with the availability of next generation sequencing, it has become tractable to describe this diversity in a meaningful manner.Our initial work in attempting to characterize the diversity of an antibody phage displayed library (Proc Natl Acad Sci 106(48):20216-21 (2009)) led to the development of methods for Roche 454 pyrosequencing of antibody genes and bioinformatics packages to analyze data from such sequencing runs.