Anion desorption stimulated by the impact of 0-20 eV electrons on O-2/hydrocarbon mixed films is reported. It is shown that part of the H-, OH-, CH-, and CH- desorption yields from O-2/hydrocarbon films is the result of reactive scattering of O-fragments produced via dissociative electron attachment (DEA) in the alkane and alkene thin films. These results support the interpretation that the DEA O- react with the hydrocarbon molecules to form a transient molecular anion complex which, in addition to autodetachment, may decay by dissociation into various anion and neutral fragments, and thus cause chemical modification of the solid.