RECENT experiments with groundnuts, Arachis hypogea, on the Muara plots near Bogor, Java, have shown that small applications of molybdenum produce a markedly beneficial effect on the colour and growth of this legume when grown on latosols of this area. The beneficial effect was not confined to one soil mapping unit in the plot field, and since latosols are widely distributed and extensive, especially in the moist tropics, the desirability of a thorough investigation of trace-element deficiency in these leached soils is indicated.