Considerable attention has been given to development of renewable energy due to imminent exhaustion of fossil fuels and environmental concerns over global warming. Bio-oil is recognized to be a promising alternative energy source because many different kinds of biomass, including agricultural residues, forest residues, organic waste, and biomass crops, can be used to produce bio-oil. In particular, agricultural residues are abundant biomass resources in South Korea that are usually composted, burned, or abandoned. In this study, the pyrolysis characteristics of two different agricultural residues, red pepper stem and garlic stem, were investigated to evaluate their potential as sources of bio-oil and chemicals for industry. Fast pyrolysis of these agricultural residues was carried out using a lab-scale reactor system. The effects of operation conditions were investigated. Analyses on the gas, liquid and solid products were performed. Pyrolysis temperature turned out to be an important parameter determining the product yields. The optimum temperature was determined to be 500 degrees C for garlic stem and 480 degrees C for pepper stem at which the bio-oil yield was 39.6 wt.% and 45.8 wt.%, respectively. The bio-oil yield increased and the char yield decreased with increasing sample particle size. (C) 2011 Elsevier Ltd. All rights reserved.