Conventional management of grow/finish pigs until recently has been to keep one or two litters in each pen in order to minimize aggression. In recent years producers have moved to sorting pigs by sex (for split sex feeding) or weight (in an unsuccessful attempt to reduce variation at marketing). However small group sizes are still retained, usually limited by the number of pigs that could be fed from a 2-4 hole feeder. With larger operations, or those that practice batch farrowing, producers are now able to form groups of several hundred pigs of similar age and gender. Advantages with larger operations are that less penning is used and the need for alleys within the room is eliminated, thus reducing some aspect of capital cost. More importantly, large groups allow us to apply new technology, particularly when it comes to sorting animals not only for market but also for phase feeding programs within each group. There is the potential for handling to be improved through the use of facilities designed for large groups, and anecdotal evidence would suggest that pigs from large groups handle and load better at marketing. However, a number of producers who have adopted large groups, particularly those using auto-sort technology, have experienced unsatisfactory results. This is common whenever new technology is tried, and solutions need to be found to the problems they are experiencing. Most of the concerns about large group sizes in the past were related to the behaviour and stability of the social structure within groups. As group size increased, social problems increased, and many producers feared that aggression, productivity, and general health of the pigs would deteriorate. This was true to a certain point, but research indicates that the nature of the social structure among animals changes in very large groups. Studies have found that aggression following regrouping is similar, when expressed as minutes per pig, in conventional groups of 10-20 and large groups of over 100. Studies have also examined how readily pigs could move into small and large groups. When pigs were added to a small group there was more fighting than when pigs were added to a large group. Large groups also make the use of auto-sort technology affordable. In such a system pigs are required to pass through a scale that directs them into different areas based on their weight. The scales are usually set up so that pigs pass through them on the way to the feeder. However, most problems associated with auto-sort systems involve pigs refusing to pass through the scale or reluctance to do it several times a day. There are two basic approaches to ‘teaching’ pigs to pass through the sorter. The first approach is to force them through to ensure that all animals have passed through the scale to the food court. The second approach involves ‘shaping’ the pigs behaviour, from that of eating in an open pen to being willing to walk through the scale to obtain feed. Some producers allow their pigs to have ready access the food court at all times with the exception of a weekly managed sort. During this time the animals are gradually moved through the scale and sorted into appropriate weight groups for the following week. The pigs are never required to move through the sorter on their own. We are still at an early stage in developing all of the management criteria for these systems, and so it is better to err on the side of the pig rather than attempting to save on equipment and space. Managing grow-finish pigs in large groups has a great deal of potential, particularly if auto-sorters are used to manage a multi-phase feeding program. Producers choosing to adopt large groups for grow-finish pigs should demand a high level of service from their suppliers, and watch for the results of recent research in the producer press.