This report results from the discussion of an Expert Group convened in Bergamo on 11-12 November 1992 for a workshop on that subject sponsored and organized by the Commission of the European Communities, Directorate General XII (CEC-DG XII). The experts taking part in the Workshop were: S. Garattini, Coordinator (Istituto di Ricerche Farmacologiche 'Mario Negri', Milano); G.N. Fracchia, Secretary (Medical Research-Pharmaceuticals, CEC-DG XII, Brussels) and the participants: L. Baroldi (Glaxo, Verona), J.P. Boissel (Hopital Neuro-Cardiologique, Dept. Methodologie et Essais, Lyon); S. Buitendijk (Dept. of Pediatrics, Neonatal Intensive Care Unit, University Hospital, Leiden); M. Buyse (Institute for Drug Development, Brussels); I. Chalmers (Effective Care Pregnancy and Childbirth National Perinatal, Epidemiology Unit, Radcliffe Infirmary, Oxford); E. Cooke (EFPIA, Brussels); B. Davis (Medicines Control Agency, Dept. of Health, London); G. de Gaetano (Consorzio Mario Negri Sud, S. Maria Imbaro); T. de Vries (WHO Collaborating Center for Pharmacology and Drug Policy, Dept. Pharmacology, University of Groningen); M. Donnelly (Commission of the European Communities, Service Pharmaceuticals, DG III, Brussels); A. Dresse (Lab. de Pharmacologie, Institut de Pathologie, Universite de Liege, Sart-Tilman-Liege); B. Dupuis (Pharmacologie-Faculte de Medecine. Lille); W. Gunnarson (Orphan Europe Sarl, Paris); B. Guy Grand (Dept. of Internal Medicine and Nutrition, Hotel Dicu, Paris); A. Heiberg (Frambu Helsesenter, Siggerud); J. Houghton (CRC Clinical Trials Centre, Kings College, Rayne Institute, London); 1. Janzon (Dept. of Commun. Health Sciences, Malmo General Hospital, Malmo); A. Lazzarini (ICI Pharma, Milano); A. Liberati (Istituto di Ricerche Farmacologiche 'Mario Negri', Milano); P. Loirat (Hopital Foch, Suresnes); A.D. Malcolm (Div. of Medical Sciences, The Wellcome Foundation Ltd., Kent); E. Marubini (Istituto di Biometria e Statistica Medica, Milano); G. Remuzzi (Laboratori Negri Bergamo, Bergamo); H. Sandholzer (George-August Universitet, Abt. Allgemeinmedizin, Gottingen); P. Simon (SANOFI Recherche, Centre de Paris, Paris); G. Tognoni (Istituto di Ricerche Farmacologiche 'Mario Negri', Milano; R. Wahlstrom (Karolinska Institute, Stockholm).