Over the past twelve years, the Centre for Medicines Research has held a series of Workshops on a number of topics related to the drug discovery and development process. The major objective of these Workshops has been to provide an international forum for regula­ tory, academic and industry representatives to debate together, and suggest solutions to, specific problems. The meeting reported in this volume represents a departure from this approach, in that the par­ ticipants were drawn largely from the pharmaceutical industry. Senior clinicians, pharmacologists and toxicologists from companies in Europe, the USA and Japan met in May 1994 to discuss a scientific rationale for the conduct of toxicity studies to support the clinical development of new medicines, and to begin to work towards an industry consensus. Achievement of such a consensus is seen as an important step in the process leading towards international harmon­ isation of the recommendations on the timing of toxicity studies in relation to clinical trials.