An aptamer is a short RNA or DNA molecule that binds to a specific target. The main strategy for obtaining aptamers is systematic evolution of ligands by exponential enrichment (SELEX). Although various SELEX techniques have been devised and refined on the basis of the selection technique used, in most cases, the isolation of an aptamer still requires several trials or the use of special equipment. In the present study, we attempted SELEX in which PCR bias was Suppressed by using RNA transcription to amplify nucleic acids. This procedure. which can be accomplished easily and inexpensively without special equipment, effectively simplifies the SELEX process. Using this SELEX, we obtained large numbers of RNA aptamers against the target that could not be isolated by standard SELEX The results of our study Suggest that exclusion of PCR bias may be far more important than previously assumed for isolating RNA aptamers via SELEX (C) 2009 Elsevier Inc. All rights reserved.