The distribution of pyrethroid insecticides in the environment was assessed by separately measuring concentrations in the dissolved and suspended sediment phases of surface water samples. Filtered water was extracted by HLB solid-phase extraction cartridges, while the sediment on the filter was sonicated and cleaned up using carbon and aluminum cartridges. Detection limits for the 13 pyrethroids analyzed by gas chromatography-tandem mass spectrometry were 0.5 to 1 ng L-1 for water and 2 to 6 ng g for the suspended sediments. Seven pyrethroids were detected in six water samples collected from either urban or agricultural creeks, with bifenthrin detected the most frequently and at the highest concentrations. In spiked water samples and field samples, the majority of the pyrethroids were associated with the suspended sediments.