Introduction. The objective of the present paper was to evaluate the effects of N, P and K, and their interactions, on fruit yield and quality of two sweet orange varieties, Valencia and Pêra, grown on tropical soils in the State of São Paulo, Brazil, over four seasons. Materials and methods. Two experiments were set up in a fractional factorial design of the ½ (4 × 4 × 4) type, with four rates of N [(30, 100, 170 and 240) kg·ha–1·year–1], P [(9, 27, 45 and 63) kg·ha–1·year–1)] and K [(24, 91, 158 and 225) kg·ha–1·year–1] applied to the soil surface during the rainy season. Functions of the type y = b0 + b11 N + b11 N2 + b2 P + b22 P2 + b3 K + b33 K2 + b12 NP + b13 NK + b23 PK were fitted for dependent variables: fruit yield and mass, juice content, and total soluble solids and acidity concentrations. Results. Maximum yield of Pêra and Valencia was attained, respectively, with N rates of (189 and 193) kg·ha–1. Fruit yield response to P and K fertilization for both cultivars was dependent on soil nutrient availability. Fruit size of Valencia trees was markedly affected by rates of K over 225 kg·ha–1. Yield of soluble solids per box of fruits (40.8 kg) decreased as leaf K concentration varied from (10 to 12) g·kg–1. Conclusion. Soil testing and leaf analysis play an important role in defining fruit yield and quality for citrus trees. The best nutritional program may vary depending on the destination of fruit to either juice production or the fresh market.