We faced some of the most important aspects of the problem of the appropriateness of ICU resources use, that are the relationship between volume of activity and mortality, the analysis of cost-effectiveness in intensive care medicine, and the monitoring of the human resource use in ICU. For this aim three different surveys were utilized: one at European level, the second at country level and, third, a regional survey. After developing a new measure of volume called ''high-risk volume'', we explored the relationship between outcome and volume, founding that such association was very strong (from 3 to 1719% decrease in ICU/hospital mortality every five extra high-risk patients treated per bed per year), and that an occupancy rate larger than 80% was associated with higher mortality. Therefore, patients in all levels of risk are better treated in high-risk volume ICUs with a reasonable occupancy rate. Analysing cost-effectiveness in intensive care medicine using a national case-mix categorized in different diagnostic groups, we identified brain haemorrhage, ALI/ARDS and surgical unscheduled patients as users a high volume of monetary resources less efficiently, while the scheduled abdominal surgery patients admitted to receive intensive care and patients on the ICU for minor organ support made the best use of the fewer resources spent. Finally, we designed a new approach to measure the rate and appropriateness of nursing resource use in ICU on a daily basis. Testing this approach on a group of general non-specialist ICUs, we found that the method was powerful enough to adequately distinguish between ''over'' and ''under-utilization'' and to identify all the theoretical scenarios of nurse/resource utilization.