For maximum value, a predicted model of an antibody-combining site should have an accuracy approaching that of an X-ray structure (1.6-2.7 A). In addition, the method by which the combining site is modelled should make no demands on the user of a sort that require arbitrary or subjective decisions to be made during the process. We have made substantial progress towards this objective and some recent results are reviewed. In addition, we describe how the modelling protocols developed can aid in the design of novel features within the antibody-combining site. The particular design example reported here suggests an approach for the introduction of metal-binding sites to create metallo-antibodies. This type of modification may be useful in the design of immunobiosensors, the induction of catalytic activity or simply as an alternative to metal chelates in the preparation of antibodies for imaging.