Paper revised from a version considered at TAC 41 by an Ad hoc Working Group on Plant Genetic Resources composed of TAC and Center representatives. The paper deals with the roles of IBPGR and the nine commodity-oriented IARCs in the international collection, evaluation, and preservation of plant genetic resources. This ad hoc group recommended the establishment of a continuing Inter-Center Working Group on Plant Genetic Resources composed of representatives of the ten centers, with a TAC observer. The continuing working group would advise TAC and the center directors on twelve specified issues. The paper includes a table of genetic resource activities at the IARCs by commodity. Agenda document at TAC 41 and TAC 42, October-November 1986, and March 1987