Deviatoric stresses acting in rock deformation can be estimated by measuring parameters connected with the dislocation microstructure, after an experimental calibration. In olivine, the available structural geopiezometers are based on dislocation curvature, dislocation density, sub-boundary size and recrystallized grain (neoblast) size. Their application in the case of olivine bearing rocks (peridotites) deformed in mantle conditions is critically assessed. The most reliable geopiezometer is the one based on olivine neoblast size. It yields values in the range of 1 kbar (1 kbar = 10 8 Pa) and over in the case of the sheared nodules in kimberlites, of 0.3- 0.5 kbar in the case of basalt nodules and in the Lanzo massif, although locally the stress can be much higher. These values are compared with those ascribed to mantle flow by various independent methods and which tend to indicate a lower deviatoric stress for asthenosphere flow (10-100bar). In the state of the art, the disagreement between this stress estimate and those in basalt nodules and in massifs, which is nearly one order of magnitude, can be explained by the various uncertainties in the estimate, thus leaving room for the possibility that the flow structures in these peridotites do represent asthenosphere conditions.