Dissolved aluminium has been determined in sea water samples from the southwestern Alboran Sea and the Gulf of Cadiz. Partial dissolution of eolian dust is responsible for the elevated levels of dissolved Al that were found in both the Western Mediterranean Deep Water (WMDW) (111.5 nM) and Levantine Intermediate Water (LIW) (86.2 nM) masses in the Alboran Sea. The Al concentration in the outflowing plume of Mediterranean water sampled in the Gulf of Cadiz is also elevated (72 nM). These enhanced signals and the differences between them are used in a three water mass system to calculate a maximum 10% contribution of Western Mediterranean Deep Water to the outflow plume, considerably less than has been previously supposed. While the synoptic nature of this study and the possibility of involvement of other water masses in the outflow plume leave scope to increase the participation of WMDW in the outflow plume, these measurements indicate the potential of a nontransient tracer in elucidating the component parts of complex flow systems. ¿ American Geophysical Union 1988