The invention relates to a platform technology for production of antigen binding polypeptides having specificity for a desired target antigen which is based on the conventional antibody repertoire of species in the family Camelidae, and to antigen binding polypeptides obtained using this technology platform. In particular, the invention provides an antigen binding polypeptide comprising a VH domain and a VL domain, wherein at least one hypervariable loop or complementarity determining region (CDR) in the VH domain or the VL domain is obtained from a VH or VL domain of a species in the family Camelidae.