The concentration of an environmental estrogen (4-nonylphenol) was determined in suspended solids and large volume water samples (501) collected from a major sewage treatment plant (STP) and two sites located on the lower Fraser River in British Columbia, Canada. The collection of suspended solids and large volume water samples was conducted concurrently using an in situ continuous flow centrifuge and solid phase extraction. The phase partitioning profile and log Koc of 4-nonylphenol were determined in the STP effluent and the Fraser River receiving environment. The data indicate the following: i) in situ continuous flow centrifugation and solid phase extraction techniques are appropriate methods for the determination of trace levels of 4-nonylphenol in suspended solids and water ii) the highest concentrations of 4-nonylphenol were measured in the STP final effluent iii) 4-nonylphenol showed preferential partitioning to the suspended solid phase in the STP effluent sample and iv) elevated levels of 4-nonylphenol were detected in the Fraser River receiving environment downstream of the STP.