The effects of four phosphorus fertilizers on the yield of leaves and fibres of Phormium tenaxForster were tested in an experiment conducted on a low-land soil of the State of São Paulo. The four fertilizers increased considerably the yield of leaves. Giving the value 100 to the yield obtained with bone meal, the values corresponding to ordinary superphosphate, treble superphosphate and Olinda-phos-phate (a rock phosphate) were 96, 87, and 75, respectively. In the yield of fibres, the positions of the four phosphates did not differ essentially from those observed in the yield of leaves.