A study was undertaken to investigate the causes of inadequate sticking at a number of abattoirs in the UK. Pigs were stunned using head-only electrical stunning. Sticking was with a 20 cm long, double edged knife, and involved either a long or short cut (undefined). Bleed out times were determined and vessels and organs examined to determine which were cut by the knife. Although stunning was effective in rendering the pig unconscious, some pigs were difficult to stick because of uncontrolled movement. The long cut was more effective in obtaining a fast bleed out (approx. 75 vs 85 sec), and cut a larger number of the major vessels and organs. The subclavia and carotid vessels were almost always severed, while the brachiocephalic, aorta and heart were cut approximately 45, 75 and 88% of the time, respectively. Improvements in stunning and the use of a long cut should reduce the possibility of a poor stick resulting in unacceptable welfare.