Background & aims: Indirect calorimetry was performed for a long time with the DeltatracII device (Datex, Finland), considered as a reference but no longer produced. This study aims at comparing the energy expenditure (EE), the volume of oxygen (VO2) and carbon dioxide (VCO2) measured by two new available indirect calorimeters, the QuarkRMR (Cosmed, Italy) and the CCMexpress (MedGraphic,USA), using three different methods of gas collection, with the DeltatracII in healthy subjects. Methods: Twenty-four healthy subjects (15 women and 9 men, age 53 15 yrs, mean BMI 25.5 7.1 kg/ m2) underwent measurements of EE with DeltatracII using canopy, QuarkRMR using canopy and CCMexpress using canopy, face tent and facemask. All measurements were performed for 10 min in random order. Results are presented as mean SD and compared by linear regression, repeated measure one-way ANOVA with Bonferroni's post hoc test and Bland & Altman test. Results: EE was 1630 340 kcal for DeltatracII and 1607 307 kcal, 1741 360 kcal, 1666 315 and 1626 336 kcal for QuarkRMR and CCMexpress with canopy, face tent and facemask, respectively (p ¼ 0.001). Compared to DeltatracII, Bland & Altman test showed a mean EE difference (2SD) of 24(220) kcal for QuarkRMR, and 111(260) kcal, 36(304) kcal, 5(402) kcal for CCMexpress with canopy, face tent and facemask, respectively. There was no systematic over- or underestimation with any device or gas collection method. Conclusion: Mean EE was similar between QuarkRMR and DeltatracII but not between CCMexpress, in any mode of gas collection, and DeltatracII. Bland & Altman test shows a large variability in EE differences with both devices compared to DeltatracII, highlighting the need for refining their accuracy. 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.