Compounds interaction on the biodegradation of n-butanol and sec-butanol mixture in a composite bead biofilter was investigated. The biodegradation rate of compounds in the exponential growth phase and stationary phase for the single compound and two compounds mixing systems was determined. The microbial growth rate and biochemical reaction rate of two compounds decreased with increasing compound inlet concentration for the single compound system. The microbial metabolic activity of sec-butanol biodegraded in the microbial growth process and biochemical reaction process was inhibited as n-butanol was introduced. This inhibitive effect was more pronounced at higher n-butanol inlet concentration and lower sec-butanol inlet concentration for the two compounds mixing system. (C) 2009 Elsevier Ltd. All rights reserved.