Raman spectroscopy is a very sensitive indicator of the structure and history of hard carbon films which have been recently used as wear-resistant coatings in thin film magnetic disk drives. In this first application of Raman spectroscopy to a working disk drive we obtain a sensitivity of 0.5 nm in the thickness of a carbon layer with respect to spatial variations. To within this sensitivity, no wear is detected in the slider track after 43000 start-stop cycles. The effect of laser heating is observed on the carbon overlayer while monitoring the disk temperature through the Raman spectrum. © 1987.