Anaerobic toxicity, biodegradability and kinetics of 2,4-dinitrophenol (2,4-DNP) and 3-nitrophenol (3-NP) were investigated. In an anaerobic toxicity assay (ATA), glucose and volatile fatty acids (VIA) were used as co-substrates. The test was operated at the temperature of 35 +/- 1 degrees C. Accumulative methane production was used to judge the inhibition level of nitrophenols (NPs) on methanogenic bacteria. No obvious inhibitory effects were detected for 2,4-DNP and 3-NP at concentrations < 25 and < 5 mg 1(-1). About 10-74% of 2,4-DNP and 60-80% of 3-NP can be removed. Anaerobic treatment is an effective method for removal of 3-NP. The degradation kinetics experiments were conducted in batch mode. The data were analyzed by nonlinear regression to estimate parameters in the Haldane inhibition equation. Parameter values estimated for 2,4-DNP and 3-NP, were 65.0 and 426.8 mg/gVSS d for maximum degradation rates; 475.9 and 7445.7 mg 1(-1) for saturation coefficients, and 16.3 and 25.6 mg 1(-1) for inhibition coefficients, respectively. (c) 2005 Elsevier Ltd. All rights reserved.