Sunflower nitrogen fertilization recommendations in South Africa are based on yield goals. In this approach, soil nitrogen supply is not taken into account with the result that nitrogen fertilization recommendations from differ ent institutions are in disagreement. Delta yield, the difference between a well fertilized crop and a zero nitrogen fertilized control, was found to be a more reliable indicator of the economic optimum nitrogen rate for maize than the yield goal, in three different countries. In seeking improved accuracy, this study was done with the aim to compare delta yield with yield goal as estima tors of the economical optimum nitrogen fertilization rate for sunflower. Reported results of fifty fertilization trials, each representing a specific year and locality, were collected, the nitrogen response curves fitted and the optimum nitrogen rates, corresponding yields and delta yields calculated. Grain yield responded to applied nitrogen significantly at only twenty-five of these trials and with the calculated optimum nitrogen rate within the limits of the applied nitrogen. Only 27% of the variation in the optimum nitrogen fertiliza tion rate was explained by yield goal compared with 87% by delta yield, making it a far more reliable indicator of the optimum nitrogen rate. The relationship between delta yield and the optimum nitrogen rate is best described by a power function: Y=X0.669 with Y the optimum nitrogen rate and X the delta yield, both measured in kg per ha.