In this paper on phosphorus fertilizers for corn the authors report the results obtained in four experiments located on different soil types of the State of São Paulo. The trials were laid out in 1957-58, but while two of them were annual, the others were conducted for two or three years, the fertilizers being applied only in the first year. In comparison with superphosphate, dicalcium (precipitated) phosphate, which was tested in three localities, was a little more effective in two and equal in one; Hyperphosphate, studied also in three trials, was inferior in one, equal in another and superior in the third; Olinda-phosphate (ground phosphorite from the State of Pernambuco), which figured in the four trials, was inferior in three and superior in one. In the experiment conducted for three years Hyperphosphate and Olinda-phosphate were much inferior to superphosphate and dicalcium phosphate during the first two years, but proved about as effective in the third year; in the two-year experiment, superphosphate was much superior to Olinda-phosphate in both years. In one of the annual experiments, located on sandy soil apparently well provided with available phosphorus, the period that followed sowing was dry and the stands, especially those of the plots with superphosphate, suffered considerable reductions; it was in that experiment that superphosphate was inferior to Hyperphosphate and Olinda-phosphate.