The performance of carbon, polyvinylalcohol (PVA) and steel microfibers on alkali silica reaction (ASR) were investigated. Two series of mortar specimens containing different amounts of microfibers were cast. One of the series was cured in accordance with ASTM C1260 test method, while other series were additionally cured at 23 degrees C in water for 14 days before standard ASTM C1260 curing period. Extended curing was found to be effective on reduction of ASR expansions in all of the mixtures containing any type of microfibers used in this study. This may be due to enhancement of matrix-microfiber bonding. ASR expansions were reduced by increasing the microfiber content in the specimens subjected to extended curing. (C) 2007 Elsevier Ltd. All rights reserved.