The use of an official drug adverse reaction assessment procedure became compulsory in France in 1984. The method proposed various qualifications for the semiologic and chronologic criteria used to ascribe a disorder to a specific drug but did not define them. Consensus meetings have been organized in order to define, in the main pathological fields, the adverse reactions themselves and the various qualifications of the criteria. This paper reports the results of meetings attended by hematologists, members of the French national network of Pharmacovigilance and representatives of Roussel Uclaf Drug Monitoring Department for drug-induced granulocyte and platelet cytopenias. Participants studied (a) the limits of the time interval between the appearance of the adverse reaction and the beginning or the end of the treatment with the suspected drug; (b) interpretation of a possible rechallenge; and (c) diagnostic value of in vitro tests proposed to confirm the responsibility of a specific drug in a granulocytic or platelet cytopenia.