*This Memorandum is based on a report (unpublished document WHO/CDD/88.27), which was drafted by the following signatories on the occasion of a meeting held in Geneva on 14-17 December 1987: P. O. Abiodun, Benin City, Nigeria; A. Baqui, Dhaka, Bangladesh; M. K. Bhan, New Delhi, India; G. Boudraa, Oran, Algeria; K. Brown, Baltimore, MD, USA; D. Candy, Birmingham, England (Chairman); J. Clemens, Dhaka, Bangladesh; J. C. Craft, Abbott Park, IL, USA; J. R. Hamilton, Montreal, Quebec, Canada; C. Lanata, Lima, Peru; J. McAuliffe, Fortaleza, Ceará, Brazil; M. Penny, Oxford, England; H. Romer, Caracas, Venezuela; R. B. Sack, Baltimore, MD, USA (Rapporteur); S. Sallon, Jerusalem, Israel; B. Torun, Guatemala City, Guatemala; S. Zaman, Lahore, Pakistan; R. E. Black, Baltimore, MD, USA (Observer); and the following members in the WHO Secretariat (Diarrhoeal Diseases Control Programme, Geneva, Switzerland): O. Fontaine, D. Mahalanabis (Secretary), and N. F. Pierce. A French translation of this article will appear in a later issue of the Bulletin. Requests for reprints should be sent to Diarrhoeal Diseases Control Programme, World Health Organization, 1211 Geneva 27, Switzerland.