Background: Blended learning, which combines internet-based platform and lecturing, is used in anaesthesiology and critical care teaching. However, the benefits of this method remain unclear. Methods: We conducted a prospective, multicentre, non-randomised work between 2007 and 2014 to study the effect of blended learning on the results of first year anaesthesia and critical care residents in comparison with traditional teaching. Blended learning was implemented in Rouen University Hospital in 2011 and residents affiliated to this university corresponded as the blended learning group. The primary outcome was the resident's results as measured with multiple-choice questions between blended learning and control groups after beginning blended learning (post-interventional stage). The secondary outcomes included residents' results between pre and post-interventional stages and homework's time. Moreover, comparison between control and blended learning group before beginning blended learning (pre-interventional stage) was performed. Results: From 2007 to 2014, 308 residents were included. For the pre-interventional period, the mean score in the blended learning group (n = 53) was 176 (CI 95% 163 to 188) whereas the mean score in the control group (n = 106) was 167 (CI 95% 160 to 174) (no difference). For the post-interventional period, the mean score in blended learning group (n = 54) was 232 on 300 (CI95% 227-237) whereas the mean score in the control group (n = 95) is 215 (CI95% 209-220) (P < 0.001). In the two groups, comparison between pre and post-interventional stages showed the increase of mean score, stronger for blended learning group (32% and 28% in blended learning and control group, P < 0.05). The average time of homework in the blended learning group was 27 h (CI 95% 18.2-35.8) and 10 h in the control group (CI 95% 2-18) (P < 0.05). Conclusions: This work suggests the positive effect of blended learning (associating internet-based learning and flipped classroom) on the anaesthesia and critical care residents' knowledge by increasing their homework's time. (C) 2017 Published by Elsevier Masson SAS on behalf of Societe francaise d'anesthesie et de reanimation (Sfar).