The quality of South African sunflower oil cake varies and often has an unacceptably low protein and high crude fibre content. Poor hullability of the seed is generally regarded as the primary cause thereof. This study examines the contribution of cultivar and environment to the variation in yield, physical seed traits and hullability. Seed of five cultivars produced at six environments was analysed: Grain yield and all the seed traits were affected by cultivar, environment and a relatively small cultivar × environment, interaction. Environmental effects caused the most variation for yield, hectolitre mass, hull content and the amount of fines produced, while the thousand seed weight and hullability were mainly affected by cultivar. The cultivar PAN 7392 had a high and stable hullability over environments indicating that breeding for such seed traits is possible. Correlation coefficients between hullability and the easily measurable seed traits were poor. Both the negative relationship between hectolitre mass and hullability and the positive relationship between the hectolitre mass and amount of fine material produced, indicate that seed with low hectolitre mass should be preferred for maximising the chance of obtaining seed of acceptable processing quality.