Different amounts of hull were removed from sunflower oilcake to obtain oilcake with a protein content of 40% (SFOC 40), 42% (SFOC 42), 44% (SFOC 44) and 46% (SFOC 46). respectively. The increase in crude protein content from 40% to 46% resulted in a concomitant increase in the  concentration of amino acids. Lysine increased from 1.21% to 1.42% and the S-containing amino acids from 1.53% to 1.89%. The concentrations of these amino acids expressed as g/100 g protein remained constant. In contrast, crude fibre decreased from 19.1% to 14.0%. The relative nutritive value (RNV), in rats, of SFOC 40 (50%) did not differ significantly (P> 0.05) from that of SFOC 46 (47%). The addition of synthetic lysine significantly (P < 0.05) improved RNV (69% for SFOC 40 and 67% for SFOC 46). True  protein digestibility was not improved (P > 0.05) by removing more hull (84% for SFOC 40 and 85% for SFOC 46) or by the addition of synthetic lysine (84% to 86% for SFOC 40 and 85% to 87% for SFOC 46). No significant differences (P> 0.05) could be found in mean growth rate (0.77 kg/day and 0.80 kg/day) and feed conversion ratio (3.1 kg/kg and 3.0 kg/kg)  between pigs that received diets formulated on an isonutrient basis using sunflower oilcake meals containing different concentrations of protein (SFOC 40 and 46, respectively). The bioavailable energy for pigs (DE) and poultry (fME and TMEn) did not differ significantly (P > 0.05) between SFOC 40 and SFOC 44.