Energy transfer from excited pyrene (donor) to proflavine (acceptor) was measured in sodium dextran sulfate/dodecyltrimethylammonium bromide (DxS/DTAB), DxS/dodecyltrimethylammonium chloride (DxS/DTAC), poly(vinyl sulfate)/DTAB (PVS/DTAB), and poly(styrenesulfonate)/DTAB (PSS/DTAB) mixed solutions by monitoring both the quenching of pyrene emission and the enhancement of proflavine emission as a function of acceptor concentration at 0.1, 0.2, 0.3, 0.4, and 0.5 mmol dm(-3) surfactant. A remarkably high enhancement of energy transfer was found in DxS/DTAB, DxS/DTAC, and PVS/DTAB complexes, but the energy transfer efficiency was low in PSS/DTAB complexes. The enhanced energy transfer is attributed to the presence of polymer/surfactant (P/S) aggregates which solubilize the donor and acceptor in monomeric form. The high energy transfer efficiency in the DxS and PVS systems is due to the larger aggregate sizes in these systems, related to the higher degree of cooperativity observed in the surfactant binding isotherm. Smaller aggregate sizes in the PSS/DTAB complex lead to a lower energy transfer efficiency. ET efficiences are relatively independent of the surfactant counterion, bromide or chloride, indicating the complete exclusion of the counterion from the surface of the P/S aggregate.