In the last 40 years, Al has been proved to play a major role in the low fertility of acid soils, and a number of methods have been developed for its determination. In this paper, the performances of a titrimetric, an atomic absorption and a colorimetric method for the determination of Al in 0.6 N BaCl2extracts of five hill soils of the humid NW Spain are compared. Two of the soils were developed on granite, one on shale, one on schist and one on gabbro and their Al content ranged between 1.3 and 3.6 cmol(+)/L.