Humid tropical mountainous soils of the Bambouto volcanic mountain (West Cameroon) have been studied mainly from a chemical view point. The aim of the study was firstly to study the behaviour of iron, aluminium and silicon during pedogenesis, and to determine the forms of the three main elements. Global balance of iron is negative; it is the result of slight illuviation at the base of the profile, and moderate eluviation in the upper horizons. Selective extractions show that iron is mainly in the 'resistant' form, more moderately in the crystallized forms, while the amorphous forms are negligible, with a quasi-absence of organic amorphous forms. Silicon is highly evacuated in all horizons. Aluminium, characterized by high accumulation at the base of the profile and moderate evacuation in the upper part, presents an excess global balance. Otherwise, contrary to iron, organic amorphous forms of aluminium are well represented in these soils, which the occurrence of aluminium permits to assimilate to Aluandosols. Humid tropical mountainous soils show pedological evolution mainly dominated by the behaviour of silicon and aluminium, with iron appearing to have a negligible role. However, contrary to the temperate soils, in which bisiallitisation is the predominant process, in mountainous soils, characterized by high evacuation of silica concomitantly to notable accumulations of aluminium, allitisation predominates. This is associated with moderate andosolisation, due to the presence of a volcanic parent rock.