Adeno-associated virus (AAV) has attracted considerable interest as a gene therapy vector over the past decade. In all, 85% of the current 2052 PubMed references on AAV (as of December 2004) have been published in the last 10 years. As researchers have moved forward with using this vector system for gene delivery, an increased appreciation for the complexities of AAV biology has emerged. The biology of recombinant AAV (rAAV) transduction has demonstrated considerable diversity in different cell types and target tissues. This review will summarize the current understanding of events that control rAAV transduction following receptor binding and leading to nuclear uptake. These stages are broadly classified as intracellular trafficking and have been found to be a major rate-limiting step in rAAV transduction for many cell types. Advances in understanding this area of rAAV biology will help to improve the efficacy of this vector system for the treatment of inherited and acquired diseases.