Pyrolysis of raw rice straw (RS), water-washed rice straw (WRS) and acid-washed rice straw (ARS) was conducted on a fixed bed reactor. A standard detergent method was used to determine the fiber constituents including neutral detergent solute (NDS), hemicellulose, cellulose and lignin in RS, WRS, ARS and their chars. Results showed that water washing removed most alkali metals (K and Na) from RS, and acid washing removed almost all alkali and alkali earth metals (K, Na, Ca and Mg); meanwhile, either washing eluted a portion of NDS but nearly unaffected hemicellulose, cellulose and lignin in RS. Attempts were made to assess the intermingled influences of the internal alkali and alkali earth metals (AAEMs) and the varied organic matter on the pyrolysis behaviors. It was revealed that the AAEMs inherent in RS had multiple impacts on the product distribution, the decomposition characteristics of fiber constituents, and the compositions of all gaseous, liquid, and char products. (C) 2012 Elsevier Ltd. All rights reserved.