Sequences of Aotus nancymaae immunoglobulin kappa light-chain rearrangements were analyzed after reverse transcription polymerase chain reaction. Among 22 in-frame rearrangements analyzed, 12 IGKV genes belonging to the families 1, 2, or 3 were identified. Aotus counterparts for all five human IGKJ genes were found. The identity of the deduced human and Aotus amino acid sequences was between 83% and 92% for junctional regions and 74% for the constant region. Sequence comparisons between rearrangements indicated that somatic mutations, the addition of nongermline-encoded nucleotides, and exonuclease trimming contribute to the generation of diversity of Aotus immunoglobulin kappa chains. The high identity of Aotus and human IGK genes is comparable to that of T-cell receptor genes and further supports the proposal to use the Aotus Plasmodium falciparum infection model for the evaluation of malaria vaccine candidates.