In 2 trials 140 male and female pigs were allowed different pen space. Groups of 4, 6, 8 or 10 pigs were given a diet with 16% protein to appetite from about 65 to 225 lb liveweight in pens which were 5 feet wide and 20 feet long. In the first trial in winter in Tennessee there were 84 pigs and in the second, the next summer there were 56 pigs. In both trials there was no significant difference among groups in gain, efficiency or depth of back fat but castrated males gained faster than females and had thicker back fat. In the second trial average daily gain was greater than in the first, 1.60 against 1.48 lb. Depth of back fat was also greater in the second trial and may have been related to differences in the breed of pig.