Six group sizes and three levels of floor area allowance were studied in a 6 x 3 factorial arrangement. Group sizes were 3,5,6,7,10 and 15 pigs per pen. Floor area allowances were 0.030, 0.039 and 0.048 m2 x BW0.667 (body weight to the power of 2/3). Initial weights averaged 25.0 kg, and pigs remained on test for 12 wk. Pigs were weighed, feed intake determined, and size of pens increased at 2-wk intervals. Pen average daily weight gain (ADG) was reduced with increasing group size (899, 851, 868, 872, 857 and 821 g 3, 5, 6, 7, 10 and 15 pigs, respectively, P < 0.05). ADG and ADF (832 g and 2.25 kg, respectively) for the most crowded space allowance were reduced compared with more spacious allowances (ADG and ADF of 875 and 877 g, and 2.35 and 2.36 kg, for 0.039 and 0.048 m2 x BW0.667, respectively; P < 0.05). These results demonstrate that group size and space allowance act independently upon productivity.