This study evaluated the effects of split marketing (Sm), whereby some pigs in a group are removed for slaughter before others, on entire male pigs and gilts. Twenty-eight single sex groups of 14 pigs (75 ± 5 kg) were assigned to the following treatments: Male-Sm, Male-Control, Female-Sm and Female-Control. Pigs were fed 3 times daily. Control pigs were all slaughtered after 6 weeks on trial, whereas in Sm groups the 3 heaviest pigs were slaughtered 2 weeks earlier. The number of fights during feeding was recorded during 2 days prior to and after Sm, the day of Sm, and 2 weeks later. Observations prior to Sm were combined, as were observations post Sm. Behavioural data were analysed using repeated measures ANOVA, and carcass characteristics were recorded and analysed by ANOVA. Split marketing reduced the coefficient of variation in carcass weight (Sm: 8.6%, Control: 10.9%; s.e=0.71, p<0.05). There were no significant differences between Sm groups (just including data from 11 remaining pigs) and Control groups in carcass weight (77.6 and 78.7 kg), backfat depth (10.4 and 10.2 mm), lean meat % (58.7 and 58.9%), and kill out % (76.1 and 75.8%). There was an interaction between gender, treatment and observation period in aggressive behaviour (p<0.01). In male groups there was a reduction in fighting between observations taken prior to and at Sm (prior Sm: 24.2, day of Sm: 14.7; s.e=1.78, p<0.05), but no difference between Control and Sm groups in any period. In female groups, the proportion of fights was higher in Control than Sm groups during the post Sm period (Sm: 13.4, control: 25.7; s.e=3.51, p=0.06). Thus, without affecting carcass characteristics, Sm reduced aggression at feeding during the post Sm period in female groups. The fact that this was not shown in male groups may reflect different social regulation.