A comparison between the efficiency of cotton fertilization by leaf spraying and usual soil incorporation was made. Experiments were conducted in 3 consecutive years (1964-1966), using the variety IAC RM3, on a "Latossolo Roxo", at Campinas, São Paulo State. Fertilin solutions, which provided N, P, K, Ca and Mg, were applied on leaves six times during the three first months of plant cycle. The possibility of complete substitution of traditional fertilization was studied. Complementary and supplementary effects of leaf fertilizer were also tested. The total yield of cotton showed evident advantageous effect of traditional manuring only. In the last experiment, however, some indications of leaf fertilizer action were noticed.