In mammals, somatic hypermutation (SHM) ofimmunoglobulin (Ig) genes is critical for the generation of high affinity antibodies and effective immune responses.Knowledge of sequence specific biases in the targeting of somatic mutations can be useful to studies aimed to understand antibody repertoires produced in response to infections, B cell neoplasms, or autoimmune disease.To evaluate potential nucleotide targets of somatic mutation in zebrafish, we constructed an enriched cDNA library of IgL VJ-C segments from which randomly selected clones were sequenced and analyzed.