An expert meeting to discuss issues relating to the design of population pharmacokinetic/pharmacodynamic (PK/PD) studies was held in Brussels in March 1995, under the auspices of the European Co-operation in Science and Technology (COST), Medicine (B1) programme. The purpose of the meeting was to discuss the experts' experience in designing and performing population PK/PD studies. The topics discussed were current practice, logistical issues, ensuring the accuracy of data, covariate assessment, communication, and protocol design. The main conclusions from the meeting were: 1) a population PK/PD analysis should be one of the objectives of a clinical trial and should not compromise the other objectives; 2) it is particularly important to communicate the purpose of the population PK/PD analysis to the investigators and to convince them of the importance of accurately recording dosing and sampling times; 3) some prior knowledge of the PK and PD models and covariate relationships is necessary for the analysis of sparse phase III data; 4) computer simulation and optimal design measures may be useful in defining sampling times; 5) population methods and objectives must be specified as completely as possible in the protocol. Participants: L. Aarons (UK), L. Balant (Switzerland), P. Bechtel (France), R. Bruno (France), P. Burtin (Switzerland), C. Dubruc (France), E. Fuseau (UK), J. Gabrielsson (Sweden), U. Gundert-Remy (Germany), R. Jochemsen (France), M. Karlsson (Sweden), C. Laveille (France), I. Meineke (Germany), F. Mentré (France), P. Morselli (France), G. Paintaud (France), A. Racine-Poon (Switzerland), J. Rodriguez (Spain), F. Rombout (The Netherlands), M. Rowland (UK), J.-L. Steimer (Switzerland), A. Van Peer (Belgium), S. Vozeh (Switzerland), W. Weber (Germany), B. Wittke (Switzerland) The views expressed by the participants do not necessarily reflect those of the organizations they represent. © 1996 Springer-Verlag.