A system and method for determining head-disk contact (HDC) in a disk drive uses the signal from the magnetoresistive (MR) read head and does not require the presence of magnetic transitions on the disk. The method thus has application in head-disk testers or "spin stands" to facilitate the design and testing of slider-suspension assemblies and fly-height actuators, as well as in disk drives to take corrective action before HDC and/or to control fly-height actuators. The invention is also a magnetic recording disk drive that has a fly-height actuator and a low-pass filter and comparator circuit for the MR signal. When the output of the filter exceeds a threshold the comparator circuit output indicates the onset of HDC. The comparator circuit output is input to a digital processor or controller. When the controller determines the onset of HDC or that HDC has occurred, it generates a control signal that can be used to cause the disk drive to take corrective action.