1. B. Lanske, K. Lee, A. Pirro, A.-B. Abou-Samra, H. Jüppner, G. V. Segre, H. M. Kronenberg, Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
2. A. C. Karaplis, Department of Medicine, Sir Mortimer B. Davis—Jewish General Hospital, McGill University, Montreal, Quebec H3T 1E2, Canada.
3. A. Luz, Institute of Pathology, GSF München, D 85758 Neuherberg, Germany.
4. A. Vortkamp, Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
5. M. Karperien and L. H. K. Defize, Hubrecht Laboratorium, Netherlands Institute for Developmental Biology, 3584 CT Utrecht, The Netherlands.
6. C. Ho, Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
7. R. C. Mulligan, Whitehead Institute for Biomedical Research, Cambridge, MA 02142, and Massachusetts Institute of Technology, Cambridge, MA 02139, USA.