This study proposed to look into the effect of the timing of mixing of sows in large groups during early gestation on sow performance by looking at three treatments of five, 19 and 33 days post-breeding.  Differences were seen shortly after mixing in the amount of injuries and cortisol levels. There was a tendency to see decreased fertility rates with lower times in the stalls before entry into pens. With early mixing there appears to be increased amounts of aggression. The study supports European guidelines of utilizing gestation stalls until after implantation before introduction of sows into pens. It has an added benefit in that sows that are found to be not pregnant are often identified before the creation of a cohort in gestation pens, thus increasing the utilization of facilities, and decreasing the likelihood of subsequent mixing events.