Barodesy is a new approach to constitutive modelling of soil. It is based on Goldscheider's principles and maps stretching directions onto corresponding stress directions with the help of a simple exponential function. This mapping also determines a critical state surface in principal stress space. The article investigates this surface and relates it to the well-known Matsuoka–Nakai failure criterion. It turns out that the difference between these two surfaces is negligible for practical applications. Copyright © 2011 John Wiley & Sons, Ltd.