A continuous flow system has been connected to a graphite furnace atomic absorption spectrometer. The system is used to determine low levels of quickly reacting Al (Al q r ) in natural waters. In the flow system, aluminium reacts with oxine for 2.3 s and the formed complex is then extracted into toluene. Iron interference is minimized with a masking buffer present in the reagent. Via a simple interface, the toluene extract is introduced into the graphite tube. Good repeatabilities (R.S.D. ca. 2%, n = 10) were obtained, both for standard solutions and for natural waters. The detection limit is < 0.5 μg l - 1 , and the sample throughput using 3 injections/sample, is ca. 10 samples h - 1 . The system has been used for determining Al q r in tap water, and is well suited for aluminium fractionation in near-neutral waters.