Since 1948 Belgium has played a leading role in the selection and breeding of the genus Populus. In the late 1960s, this work resulted in the Unalclones, combining the most desired clonal properties. In this paper attention is given to the most important poplar diseases in Europe (i.e. poplar canker Xanthomonas populi, and rusts Melampsora species), how breeding and selection may result in broadly disease resistant clones, and the possible negative influence of these diseases on poplar growth and wood quality. Copyright (C) 1996 Elsevier Science Ltd.