To measure the impact of implementation of the systematic evaluation of pain and agitation by nurses using the Behavioral Pain Scale (BPS), the Numerical Rating Scale (NRS) for pain, and the Richmond Agitation Sedation Scale (RASS) associated with medical staff education in analgesia and sedation management in intensive care unit (ICU) patients. Two-phase, prospective, controlled study. Twelve-bed medical-surgical ICU in a university hospital. Consecutive patients staying >24 hrs in ICU. BPS, NRS, and RASS were measured twice daily, at rest, by independent observers during 21 wks (control group) and after 4 wks of training, by nurses during 29 wks (intervention group). In the intervention group, the treating physician was alerted in case of pain defined by BPS>5 or NRS>3 or in case of agitation defined by RASS>1. A total of 230 patients were included (control group, n=100; intervention group, n=130). Baseline characteristics were not significantly different. The incidence of pain and agitation decreased significantly in the intervention group: 63% vs. 42% (p=.002) and 29% vs. 12% (p=.002), respectively. Rate of severe pain and agitation events defined by NRS>6 and RASS>2, respectively, also decreased significantly. There were significantly more therapeutic changes in the intervention group in the way of an escalation but also in the way of a de-escalation for analgesic and psychoactive drugs. Compared with the control group, there was a marked decrease in the duration of mechanical ventilation (120 [interquartile range 48-312] vs. 65 (24-192) hrs, p=.01) and nosocomial infections rate (17% vs. 8%, p<.05) in the intervention group. There was no significant difference in median length of stay (9 [4, 15] vs. 7 [4, 13] days) and mortality in ICU (12 vs. 15%). Systematic evaluation of pain and agitation, and analgesics and sedatives need was associated with a decrease in incidence of pain and agitation, duration of mechanical ventilation and nosocomial infections.