A theoretical solution for the indentation of a layered medium by an axisymmetric plane-ended ram has been applied in the in vitro study of the mechanical properties of the articular surface of the distal femur of the rabbit. Experimental results directly yield shear moduli and retardation spectra which are invariant with respect to cartilage thickness and applied stress within the stress range used. The success of this theory, coupled with the simplicity and reproducibility of the test, suggests that this method has wide applicability in the study of experimentally or pathologically altered cartilage.