Weathering of ultramafic rocks from the Sipilou and Moyango areas of the western Ivory Coast was studied from a series of profiles distributed along a topographic slope from upper plateau zones to lower slopes (catena profiles). The distribution, thickness, and composition of the different weathering layers vary according to their location, i.e. whether they are on the plateau, on the hillside, or in the lower areas. Nickel distribution follows these vertical and horizontal variations. The highest nickel contents are linked to the distribution of secondary phyllosilicates (principally talc and smectites) which are generated by the weathering of olivines, pyroxenes, and serpentines. In general, ferruginous layers are the most developed in the plateau areas, where extensive silicification exists on the hill slope. The accumulation of carbonates takes place downslope and at the bottom of the weathering profiles.