Hot water extraction of bitumen from Alberta oil sands generates large quantities of tailings slurry. The fine grained sludge component of this waste is the most troublesome because of its stability and poor compaction potential. Dispersed bitumen, and organic matter that is insoluble in common solvents (IOM), are associated with the fines contained in these clay slimes. This organic matter is believed to be partly responsible for the intractability of the sludge, and it could therefore play an important role in determining the behavioural characteristics of oil sands slimes. In this investigation the settling behaviour of the sludge was studied after removal of emulsified bitumen by an oil phase agglomeration technique. After partial removal of bitumen the sludge was fractionated into settling and non-settling fractions. The insoluble organic matter associated with the clay fines present in the non-settling portion of sludge was concentrated by dissolving the mineral matter in . These fractions were analysed using elemental analysis and solid state 13C n.m.r. spectroscopy. The elemental analyses were discussed in terms of a van Krevelen diagram by plotting atomic ratios against atomic ratios. N.m.r. data were used to calculate the aromaticities of the various organic fractions. Based on the n.m.r. data, it is suggested that the IOM associated with sludge solids is derived from the parent oil sand feed.