Monoclonal antibodies were prepared which react with members of the high-tyrosine type proteins from Merino wool. Specificity was confirmed by the use of Western transfer immunoassays and by enzyme-linked immunosorbent assay on purified fractions. Immunofluorescent staining of sections of wool follicles using the antibodies showed that the proteins were present in the developing wool shaft but that staining was asymmetric, indicating specific location of the proteins in the orthocortex of the fibres. Immunogold-electron microscopy confirmed that one of the antibodies bound to the keratin microfibril bundles.