Analysis of the distribution of gibbsite in soils and saprolites of Galicia, NW Spain, leads to the conclusion that this mineral is mostly formed by inorganic mechanisms in open, well-drained and desaturated systems in the initial stages of weathering of various aluminosilicates, especially plagioclases. No evidence has been found to support the hypothesis that it is a feature inherited from hotter climates, as it has not been identified to date either in ancient sediments or in the most evolved and weathered soils. The role of organic matter and the possibility ofa biogeochemical origin is also discussed: it is considered that this mechanism is only important during podsolic soil development.