This review discusses recent trends in chemical speciation of aluminium in natural waters. Several difficulties which arise from the complexity of aluminium species present in natural samples as well as its participation in dynamic equilibrium are highlights. Taking this into account various approaches for speciation of Al described in the literature are critically evaluated. The strategy of fractionation procedures based on the rate of reaction, sorption efficiency, chromatographic behaviour of the aluminium compounds or size of the molecules are described in the paper. Besides conventional procedures involving various measuring and separation techniques, a special emphasis is focused on mechanised flow injection methodologies. This was found to be very important in order to ensure precise control of the reaction time. which is essential in aluminium species equilibrium system. The analytical performance of several separation procedures based on flow injection approaches as well as the detection methods are discussed and compared. (C) 1999 Elsevier Science Ltd. Ail rights reserved.