Uptake of four pesticides-the organochlorines chlordane and endosulfan and the synthetic pyrethroids fenvalerate and allethrin-by triolein-containing semipermeable membrane devices (SPMDs) and by the lake mussel Anodonta piscinalis was studied in a laboratory continuous-flow system. Uptake of the analytes by the SPMDs and mussels was linear during the exposure period of 20 d. These kinetic data were used to calculate the first-order uptake rate constants. On a SPMD-whole body basis, the uptake rates were 3.5 to 5.5 times higher in the membrane devices than in the organisms. The synthetic pyrethroids were sampled at lower rates than the organochlorines, and this difference may be attributed to the larger molecular dimensions of the pyrethroids rather than analyte molecular weight and lipophilicity, which were similar for all test compounds. Because of the disparate sampling rates, concentration factors of analytes differed between SPMDs and mussels. However, the percent composition (ratios) of analytes in SPMDs and in mussels was similar, which indicates that SPMDs may serve as good surrogates for aquatic organisms with respect to the discriminatory uptake of hydrophobic chemicals. Semipermeable membrane device dialysate, mussel extract, as well as two artificial mixtures of the four pesticides were tested with standard toxicity and genotoxicity tests, including Microtox (inhibition of bacterial luminescence), Daphtoxkit, and Rotoxkit (toxicity tests with freshwater invertebrates Daphnia pulex and Brachionus calyciflorus, respectively), and sister chromatid exchange in human lymphocytes in in vitro assay. Results of these tests suggest that integration of the SPMD technique and bioassays may be a valuable approach for the assessment of levels and effects of bioavailable hydrophobic pollutants.