Abstract A high-resolution anion exchange analyzer was adapted for determination of u.v.-absorbing compounds in water at μg 1 −1 levels. The samples were concentrated prior to analysis by vacuum distillation and freeze-drying. Seventy-seven peaks were obtained from a municipal primary sewage effluent; each constituent was present at less than 100 μg 1 −1. Thirty-eight peaks were obtained from a municipal secondary sewage effluent, with each constituent at less than 20 μg 1 −1. Thirteen compounds have been identified as relatively stable to primary treatment. The concentrations of compounds in industrial primary and secondary effluents were estimated at up to 1 mg 1 −1; the secondary treatment caused little degradation. Chromatograms of the effluents appear to depend upon sewage plant operating conditions as well as upon the type of feed sent to the treatment plant.