Excitation functions of fluorescence of complex organic compound vapors by a monokinetic energy-tuned electron beam are studied. It is shown for the first time that the maximum of these functions is in the region of - 4ETwhere ETis threshold excitation energy of a lower singlet state. Emission spectra have been recorded for POPOP molecules at collision with high-energy electrons. Analysis of the spectra, as well as of the character of excitation functions changes enabled us to draw a conclusion about weak destruction of complex organic molecules as a result of direct electron impact.