Two comparative slaughter experiments, Trials 1 and 2, were conducted to evaluate the utilization of metabolizable energy (ME) by young pigs raised in groups and to compare the energy utilization of pigs confined individually with pigs kept in groups. The influence of dietary energy density on weanling pig performance, carcass composition and energy and N utilization was also studied. Energy density was reduced by substituting solka floc for either soybean oil, Trial 3, or corn starch, Trial 4;In Trail 1, 64 weanling pigs were kept in groups of four and fed individually every 12 hours. The daily ME requirement for maintenance (MEm) was calculated to be 115 kcal/kg('.75). Above maintenance, ME was utilized for carcass energy gain with an efficiency of 50%;Trial 2 examined the energy and N utilization of weanling pigs kept either individually in cages or in groups of four under pen conditions. When compared with the individually caged pigs, the grouped pigs showed lower apparent digestibility of energy (P < .05) of ME and digestible N utilization for carcass energy and N gains. Estimates of the daily MEm for the individually confined and the grouped pigs were 138 and 101 kcal/kg('.75), respectively. The ME of the diet was utilized for net energy with an efficiency of 64 and 51% by the individually confined and grouped pigs, respectively;In Trial 3, decreasing the ME content of the diet from 3473 to 2890 kcal/kg resulted in a linear (P < .01) increase in daily feed intake to levels supporting similar ME intakes and daily gain on all treatments. The efficiency of feed utilization for gain decreased linearly (P < .01) while ME utilization for gain improved linearly (P < .01) while ME utilization for gain improved linearly (P < .01) as the ME concentrations were reduced;Reducing the ME concentration from 3303 to 2867 kcal/kg in Trial 4 did not significantly (P < .05) influence daily gain, feed intake, feed to gain, plasma urea N or rate of passage. The ratio of ME intake to gain decreased linearly (P < .01) as energy density was reduced. The carcass percentages of dry matter (P < .01), ether extract and energy (P < .05) decreased linearly as the energy density was decreased. The efficiency of ME and digestible N utilization for carcass energy and N gains were not affected by the ME concentration of the diet.