Large volumes of oil sands process-affected water (OSPW) are produced by the surface-mining oil sands industry in Alberta. The industry is following a no-release practice for OSPW due to its potential environmental toxicity. Both laboratory and field studies have demonstrated that OSPW is toxic to a variety of organisms including bacteria, invertebrates, fish, amphibians, birds, and mammals. Naphthenic acids (NAs) are widely considered as the major toxic components of OSPW, exhibiting their toxic effects through multiple modes of action such as narcosis, endocrine disruption, and carcinogenicity. However, other pollutants present in OSPW, including polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene, and xylenes (BTEX), phenols, dissolved ions, heavy metals, and other unknown constituents may also contribute to or modify the overall OSPW toxicity. Although specific information on the toxicity of the compounds present in OSPW is limited, they have been associated with a wide range of biological dysfunctions in exposed organisms, such as mutagenicity, carcinogenicity, immunotoxicity, and endocrine disruptive effects, caused by the organics (e.g., PAHs, phenols), and ionic imbalances induced by the high levels of total dissolved solids and salts. This report reviews the adverse effects of individual compounds, or mixtures of compounds, that are present in OSPW and/or other oil-related sources. Data on the additive, synergistic, and/or antagonistic effects caused by different constituents present in OSPW are not available, at present.