Purpose: It is unknown whether protocols targeting systematic prevention and treatment of fever achieve lower mean body temperature than usual care in intensive care unit (ICU) patients. The objective of the Randomised Evaluation of Active Control of temperature vs. ORdinary temperature management trial was to confirm the feasibility of such a protocol with a view to conducting a larger trial. Methods: We randomly assigned 184 adults without acute brain pathologies who had a fever in the previous 12 h, and were expected to be ventilated beyond the calendar day after recruitment, to systematic prevention and treatment of fever or usual care. The primary outcome was mean body temperature in the ICU within 7 days of randomisation. Secondary outcomes included in-hospital mortality, ICU-free days and survival time censored at hospital discharge. Results: Compared with usual temperature management, active management significantly reduced mean temperature. In both groups, fever generally abated within 72 h. The mean temperature difference between groups was greatest in the first 48 h, when it was generally in the order of 0.5 °C. Overall, 23 of 89 patients assigned to active management (25.8%) and 23 of 89 patients assigned to usual management (25.8%) died in hospital (odds ratio 1.0, 95% CI 0.51-1.96, P = 1.0). There were no statistically significant differences between groups in ICU-free days or survival to day 90. Conclusions: Active temperature management reduced body temperature compared with usual care; however, fever abated rapidly, even in patients assigned to usual care, and the magnitude of temperature separation was small. Trial Registration: Australian and New Zealand Clinical Trials Registry Number, ACTRN12616001285448.