The primary objectives of this study were to evaluate the ecological characteristics of wetland ecosystems that had developed in response to oil sands effluent relative to reference wetland ecosystems and, from such an evaluation, to assess whether these wetlands were viable systems capable of integrating into the northern Canadian landscape. A secondary objective was to evaluate the use of several ecologically relevant endpoints as indicators of an ecosystem response to a known anthropogenic stress, in this case, wetlands receiving oil sands effluent. To achieve this, a suite of endpoints were compared between effluent-impacted wetlands and nonimpacted reference wetlands. Endpoints for comparison included: (1) benthic macroinvertebrate community structure, (2) chironomid density and biomass, (3) the incidence of chironomid mentum deformities, (4) the muta- genetic potential of sediment-dwelling chironomids, (5) growth and photosynthetic rate for the aquatic plant Typha latifolia (cattail), and (6) fish acute lethality and stress response as measured by changes in blood chemistry (percentage hematocrit [%hct], percentage leucocrit [%lct], and differential white blood cell count). Wetlands receiving oil sands effluent supported a low-diversity benthic community, dominated primarily by the Chiro- nomidae and cattail. There was no evidence of mentum deformities or mutagenicity in chironomids sampled from the oil-impacted wetlands. Cattails grown in oil sands effluent and sediment demonstrated increased photosynthetic rates; however, these increased rates did not translate into increased plant growth. In contrast to the benthic community and the cattail, indigenous fish were unable to survive in wetlands containing oil sands effluent. Fish displayed altered blood chemistry (elevated %hct, depressed %lct) and ultimately death when held beyond 14 d in the oil-impacted wetlands. Of the various ecological endpoints measured, the macroinvertebrate community and changes in fish blood chemistry were the most sensitive indicators of an anthropogenic stress, demonstrating distinct differences in response between impacted and reference wetlands. To ensure that these wetlands can safely integrate into the northern Canadian landscape, future studies need to focus on their impacts at higher trophic levels indigenous to the wetland.