The invention concerns a method of testing the installation quality of a grouted anchor system comprising at least one tendon anchored by grout in a hole in a surrounding mass. The system typically includes a group of roof bolts (10, 12) each having a tendon (10.1, 10.2) anchored in a rock mass (22) by grout (14, 16). The method includes the steps of applying an acoustic signal to the system, detecting the acoustic response(s) of the tendon(s) and assessing the installation quality of the tendon(s) from an analysis of such response(s). The invention also includes apparatus for use in the method.