Eleven patients are described in whom myelomatosis was complicated by the laboratory and clinical features of the hyperviscosity syndrome (HVS). The myeloma type was IgA in nine and IgG3 in two. In those patients with IgA myeloma the HVS was related to the presence of high molecular weight complexes in the serum. Remission of clinical features was obtained in all patients by plasma exchange. Clinical improvement coincided with reduction of whole blood viscosity and in those patients with IgA myeloma, with a parallel reduction of the high molecular weight complexes. The relationship between the IgA complexes and blood viscosity has been examined by physicochemical analysis of purified IgA monomer and polymers and evidence is presented to show that the IgA polymer has a higher intrinsic viscosity and axial ratio than the larger IgM molecule. The significance of these observations is discussed.

involved in the action of peptide hormones, startling in its breadth of coverage. Professor Catt came armed with no less than 6 other seminars -a remarkable achievement. The greatest demand was for those on angiotensin and aldosterone, as well as those on the gonadotrophin-releasing hormones. He had detailed laboratory discussions with between 5 and 12 endocrine investigators each day, and all remarked on his perspicacity and helpfulness in discussing their research. Professor Catt proved to be indefatigable, despite what a distinguished British professor described as 'an itinerary for his destruction', and the educational value of his visits to young British researchers proved immense. Perhaps his only moments of peace and quiet were on a train, or when staying at the Domus Medica. He was, of course, entertained by the Clinical Endocrinology Trustees and also by the officers of the Section of Endocrinology.The value of such visits, however, is not just oneway, and is well exemplified by Professor Catt's remark to me that he had not previously realized how well focused is British endocrine research, nor how diverse. British endocrinology and the Section of Endocrinology in particular express their gratitude to Professor Catt and the Trustees for making such a marvellous visit possible.

Summary Mk was demonstrated in three generations of an English family. The propositus was detected as a result of an incompatibility in cross‐match. General serological, biochemical and biophysical aspects have been studied.

Summary. ‘Naturally occurring’ anti‐D has been studied in four Rh(D) negative males. The presence of this anti‐D does not preclude successful deliberate immunization of Rh(D) negative volunteers; ‘naturally occurring’ anti‐D does not provide a marker of non‐responders to Rh immunization. ‘Naturally occurring’ anti‐D is not necessarily the result of materno‐fetal transfusion at birth.

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