The cynomolgus macaque, Macaca fascicularis, is frequently used in immunological and other biomedical research as a model for man; understanding it's antibody repertoire is, therefore, of fundamental interest. The expressed variable-region gene repertoire of a single M. fascicularis, which was immune to the Ebola virus, was studied. Using 5' rapid amplification of cDNA ends with immunoglobulin (Ig)G-specific primers, we obtained 30 clones encoding full-length variable, diversity, and joining domains. Similar to the human V(H) repertoire, the M. fascicularis repertoire utilized numerous immunoglobulin heavy variable (IGHV) gene fragments, with the V(H)3 (41%), V(H)4 (39%), and V(H)1 (14%) subgroups used more frequently than the V(H)5 (3.9%) or V(H)7 (1.7%) subgroups. Diverse immunoglobulin heavy joining (IGHJ) fragments also appeared to be utilized, including a putative homolog of JH5beta gene segment identified in the related species Macaca mulatta, Rhesus macaque, but not in humans. Although the diverse V region genes in the IgG antibody repertoire of M. fascicularis had likely undergone somatic hypermutations (SHMs), they nevertheless showed high nucleotide identity with the corresponding human germline genes, 80-89% for IGHV and 72-92% for IGHJ. M. fascicularis and human V(H) genes were also similar in other aspects: length of complementarity-determining regions and framework regions, and distribution of consensus sites for SHMs. Finally, we demonstrated that monoclonal antibodies (mAbs) specific for an Ebola protein could be obtained from M. fascicularis tissue samples by phage display technology. In summary, the study provides new insight into the M. fascicularis V region gene repertoire and further supports the idea that macaque-derived mAbs may be of therapeutic value to humans.