Abstract: A method and device for measuring the deformation capacity of microscopic objects, more particularly, red blood corpuscles includes an enclosure comprising two mobile, coaxial, cylindrical walls which can rotate relative to one another. The objects to be measured are put into a liquid suspension and then placed between the two walls. An optical system directs a beam of light through the suspension and the diffraction characteristics of the undeformed objects may be observed and recorded. The cylindrical walls are then driven at different rotational speeds with respect to their common axis, and the diffraction characteristics of the deformed objects are observed and recorded. The deformation of the microscopic objects can be determined as a function of the relative speed of the walls by comparing the diffraction characteristics of the objects in their undeformed and deformed states.