<p>Calculating the effect site concentration of remimazolam intraoperatively facilitates the prediction of the time from the end of remimazolam administration until the effect site concentration returns to the level at loss of consciousness (LOC). We hypothesised that the effect site concentration of remimazolam at LOC could be an indicator of arousal. This prospective, observational, single-centre study enrolled 107 patients who underwent laparoscopic surgery under remimazolam general anaesthesia. Sedative [bispectral index (BIS^®) and SedLine^®], non-invasive cardiac output (estimated continuous cardiac output^®), and effect site concentration of remimazolam monitoring were assessed simultaneously. The intraoperative remimazolam dose was adjusted to obtain the spectral edge frequency 95 (SEF) &lt; 16 on SedLine^®. The primary endpoint was the relationship between the time for the effect site concentration of remimazolam to return to its level at LOC and recovery of consciousness (ROC). The median time from recovery of the effect site concentration of remimazolam to its level at LOC until ROC was 4.0&#xa0;min. In the multivariate-adjusted general linear model, maintenance administration time and the effect site concentration of remimazolam ratio were significantly associated with the interval between effect site concentration of remimazolam recovery to LOC levels until ROC. This interval was significantly longer in patients whose effect site concentration of remimazolam ratio was lower. The effect site concentration of remimazolam at LOC could be useful for determining arousal time. The effect site concentration ratio and surgery duration could affect the time from recovery of effect site concentration of remimazolam to LOC levels until ROC.</p>