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The possibility that biological nitrogen fixation (FBN) may supply part of the N to the sugarcane plant is causing some farmers to stop or reduce fertilizer N application. The objective of the study was to evaluate the stems and shoots yields, the concentrations and content of nutrients in sugarcane, in areas fertilized and unfertilized with N for three years. Three areas of high fertility Nitosols at Aparecida Farm, located in Mogi Mirim, SP Brazil, were selected. In this farm several fields received PK fertilizers but not N in the last three years. Controlled plots in the midst of the fertilized areas received 100 kg ha-1 N as urea. In three fields with uniform plant stands, replicated (4) plots of fertilized and non fertilized adjacent areas, consisting of four cane rows 15 m long, were harvested and the dry mass and nutrient contents of the above ground parts of the plants were evaluated. Stalk yields from non-fertilized areas varied from 75 to 91 t ha-1 (fresh weight), with an average yield of 85 t ha-1. The corresponding figures for the fertilized plots were 92 to 97 t ha-1, with an average of 95 t ha-1, significantly higher than those of the non fertilized plots. The N concentration in stalks (1.4 x 2.3 g kg-1) and stalk dry matter yields (25.3 x 29.0 t ha-1) were also higher in the fertilized areas. In addition, the N content of shoots and N exported by stalks were lower in non fertilized areas (48 kg ha-1 and 35 kg ha-1, respectively) than for the fertilized areas (75 kg ha-1 and 66 kg ha-1, respectively). The data showed that the lack of N application is causing the yields and N content of the plants to decrease and that the natural N fixing microbiota could not supply all the N needed by sugarcane in these fields.ഀ