An anti-IL-12 antibody that binds to a portion of the IL-12 protein corresponding to at least one amino acid residue selected from the group consisting of residues 15, 17-21, 23, 40-43, 45-47, 54-56 and 58-62 of the amino acid sequence of the p40 subunit of IL-12, including isolated nucleic acids that encode at least one anti-IL-12 antibody, vectors, host cells, transgenic animals or plants, and methods of making and using thereof have applications in treating IL-12-related disorders, such as psoriatic arthritis.