Critically ill patients are at high risk for death and permanent disability. Their care is also very expensive. The method of delivering critical care services to these patients can have an impact on their clinical and economic outcomes. Researchers face significant challenges when attempting to identify an association between an intensive care unit (ICU) organizational characteristic and patient outcomes. In this paper we review the challenges faced when evaluating the impact of ICU organizational characteristics on patient outcomes and highlight ICU characteristics that are consistently associated with improved patient outcomes. These characteristics include: (i) the presence of specialist physicians devoted to the ICU; (ii) increased nurse : patient ratios; (iii) decreased use of tests and evaluations that will not change clinical management; (iv) development and implementation of evidence-based protocols and guidelines; (v) use of computer-based alerting and reminding systems; and (vi) having a pharmacist participate in daily rounds in the ICU. When implementing these in ICUs, it is important to evaluate the impact of these characteristics on patient outcomes. We provide a format for such an evaluation. Given the growing evidence supporting the association between specific ICU characteristics and improved patient outcomes, we hope the future realizes broad implementation of these beneficial characteristics.