Geotechnical engineers have traditionally limited their classification and behavior characterization of clays to Atterberg limits determination and calculation of an associated clay “activity” that relates the plasticity of a clay to the percentage of clay size particles present in a given sample. This paper explores the possibilities for use of methylene blue index testing to enhance geotechnical understanding of the impact of the cation exchange capacity of clays present in oil sands ores and both solid and fluid components of the tailings stream. The paper provides a basic description of the methylene blue index test procedure most commonly used for characterization in the oil sands industry, discusses requirements for obtaining consistent test results, and explores how the test has been used to enhance geotechnical characterization of clays in other areas. Potential for developing correlations between methylene blue index test results and other geotechnical parameters or index tests used to characterize solid phase and fluid fines oil sands tailings is also discussed.