This paper reports the results of three experiments located on soils extremely low in fertility of the State of São Paulo. The yields of the untreated plots were very poor. Liming was highly effective in two of lhe trials, but had no effect in lhe other. Lime and dolomite gave equivalent results. In two of the experiments the effect of a mineral NPK-fertilizer was very good and did not depend on the presence of lime; in the other, however, it was appreciable only when applied on limed and manured soil. In lhe last-mentioned experiment, the only one in which manure was tested, its effect was small where it was used alone, but the presence of lime and NPK. enhanced it considerably. Based on these experiments the authors discuss methods of improving soils similar to those studied.