Twelve contemporary U.K. sewage sludges were analysed by a Soxhlet extraction, column clean-up and capillary gas chromatography method. All the chlorobenzenes were detected in the sludges, although their content varied widely between different sewage works. Generally, chlorobenzene concentrations decreased with increasing level of compound chlorination. Sewage sludges from industrial areas generally had higher chlorobenzene concentrations than those from urban areas. Chlorobenzene concentrations in sludges from the same waste water treatment works over time were quite consistent.