Populus is a model system for investigating the wood development, crown formation, and disease resistance in perennial plants. AR2/ERF is a large family of transcription factors in plant, encoding transcriptional regulators with a variety of functions involved in the developmental and physiological processes. Here, starting from database of Populus genome, we identified 200 AP2/ERF genes by in silica cloning method using the AP2/ERF conserved domain amino acid sequence of Arabidopsis thaliana as probe. Based on the number of AP2/ERF domains and the function of the genes, those AP2/ERF genes from Populus were classified into four subfamilies named the AP2, DREB, ERF, RAV, and a soloist. Among these genes, the number genes of total AP2/ERF family genes, DREB subfamily, and ERF subfamily from Populus trichocarpa were about 1.4-1.6-fold than those from A. thaliana. The rates were very similar for the putative homologs between Populus and Arabidopsis. Crown copyright (C) 2008 Published by Elsevier Inc. All rights reserved.