Amorphous hydrogenated carbon (a-C:H) films in the thickness range 1-20 nm were deposited at 300 K on a Pt(1 1 1) single crystal by means of the ion-beam deposition (IBD) method. The product distribution as well as the temperature and thickness dependence of the hydrogen-atom-induced chemical erosion was investigated by mass spectrometry. Using an atom flux of similar to 10(16) H cm(-2) s(-1), the maximum of the erosion of a-C:H was observed at similar to 750 K, with a yield of similar to0.01 C/H. At higher temperatures, the erosion:rate decreases due to the thermally activated dehydrogenation of a-C:H. The main products of the hydrogen-atom-induced erosion reaction are C-1 (methane), C-2 (ethene, ethane), and C-3 (propene, propane) hydrocarbon species, which contribute to similar to 98% of the observed erosion rate. Higher hydrocarbon species, C-4 to C-8, were detected as minority species.