Amorphous C:D (or C:H) films were deposited on the inner surface of a spherical ultrahigh vacuum chamber by means of a direct current glow discharge in a similar to 75% D-2 (or H-2) and similar to 25% CD4 (CH4) gas mixture. Laser Raman spectroscopy analysis of the him exhibited the absence of a diamond peak at 1334.3 cm(-1). The general appearance of the spectra was indicative of a polymerlike film. Upon exposure of the C:D film to O-18(2), almost all of the released deuterium was seen to be in the (D2O)-O-18 chemical form, with less than 1% released as D-2. (CO2)-O-18 was observed to be the main C-containing reaction product of the O-18(2) exposure. No methane release was detected. x-ray photoelectron spectroscopy and secondary ion mass spectroscopy analyses of the films indicated the appearance of carbonyl groups (>C=O) and an increase in the concentration of hydroxyl groups (-COD) due to surface oxidation. The generally accepted scheme for simple thermal oxidation of hydrocarbon polymers was used to provide a plausible reaction mechanism leading to emissions of the reaction products D2O, CO2, and CO.