PURPOSE OF REVIEW: This review will highlight recent data evaluating the role of parenteral nutrition and calorie delivery in the intensive care setting. Specific focus will be placed on recent trials of early and/or supplemental parenteral nutrition (SPN) and optimization of calorie delivery in ICU patients on the basis of nutrition risk and acuity of illness. The potential key role of protein delivery in outcome will also be discussed. RECENT FINDINGS: Recent randomized clinical trial (RCT) evidence reveals conflicting results around the use of SPN utilized to augment insufficient enteral nutrition. These trials had significant differences with regard to acuity of illness (mortality risk), method of calorie delivery, and protein intake. Recent observational trials reveal a patient's preillness nutrition status and adequacy of protein intake may be vital determinants of the effect of SPN and optimal calorie delivery on outcome. SUMMARY: The conflicting results of recent RCTs of SPN have provided clarity into the factors defining which patients may benefit from additional calories/protein and which may not. These data, combined with key, large observational studies elicit a clear call to action for trials examining the benefit of optimal calorie/protein delivery in high mortality risk, high preillness nutrition risk patients.