Thirteen years after the patient's death, tissues removed at biopsy and autopsy from a case of Waldenström's macroglobulinaemia have been shown to contain intranuclear inclusion bodies composed mostly of IgM-kappa immunoglobulin. They were demonstrated by staining the tissues by peroxidase-antiperoxidase methods. A few intranuclear inclusions stained for IgG and for lambda light chains. These findings suggest that the patient's condition may have been initially polyclonal and benign, but had become virtually monoclonal and neoplastic at the time of death 23 months later. The findings lend a little support to the suggestions of other workers that the Dutcher-Fahey inclusion body is unlikely to be specific for macroglobulinaemia. Nevertheless, these inclusion bodies appear to be pertinent to the assessment of this case, in view of the marked bias towards IgM-kappa monoclonal gammopathy, which was not evident from a study of the cytoplasmic staining results alone.