The third international symposium organized by the Esteve Foundation was held on October 12-15, 1988 in Majorca and focused on dose-response relationships in clinical pharmacology. This finding, i.e. a clear relationship between the dose or concentration of a drug and a given effect, is considered to be a reliable way of attributing the action of the drug. The study of this relationship allows both an in-depth approach to the characteristics of the drug and the quantitation –or even the prediction– of possible effects of non-assessed doses. Professors Lasagna, Erill and Naranjo coordinated this scientific meeting and edited the book gathering all submissions and respective discussions (volume number 3 of Esteve Foundation Symposia).